Charcoal from the dwelling level of the Lascaux Cave in France gives an average count of 0.97 disintegrations of ^14 C per minute per gram of sample. Living wood gives 6.68 disintegrations per minute per gram. Estimate the date of occupation and hence the probable date of the wall painting in the Lascaux Cave. Hint: Disintegrations per minute per gram" has the same units as the time-derivative of concentration for a radioactive decay model. (You may use the fact that the half-life of ^14C is 5568 years.)

Answers

Answer 1

Answer:

Explanation:

count given by old sample = .97 disintegrations per minute per gram

count given by fresh sample = 6.68 disintegrations per minute per gram

Half life of radioactive carbon = 5568 years

rate of disintegration

dN / dt = λ N

In other words rate of disintegration is proportional to no of radioactive atoms present . As number reduces rate also reduces .

Let initial no of radioactive be N₀ and after time t , number reduces to N

N₀ / N = 6.68 / .97

Now

[tex]N=N_0e^{-\lambda t}[/tex]

[tex]\frac{N}{N_0} =e^{-\lambda t}[/tex]

[tex]\frac{6.68}{.97} = e^{\lambda t}[/tex]

λ is disintegration constant

λ = .693 / half life

= .693 / 5568

= .00012446 year⁻¹

Putting the values in the equation above

[tex]\frac{6.68}{.97} = e^{.00012446\times t}[/tex]

[tex]6.8866 = e^{.00012446\times t}[/tex]

1.929577 = .00012446 t

t = 15503.6 years .  


Related Questions

Phosphorus pentafluoride, PF5, acts as a __________ during the formation of the anion PF−6. Select the correct answer below: A. Lewis acid B. Lewis base C. catalyst D. drying agent

Answers

Answer:

Lewis acid

Explanation:

In chemistry, a Lewis acid is any chemical specie that accepts a lone pair of electrons while a Lewis base is any chemical specie that donates a lone pair of electrons.

If we look at the formation of PF6^-, the process is as follows;

PF5 + F^- -----> PF6^-

We can see that PF5 accepted a lone pair of electrons from F^- making PF5 a lewis acid according to our definition above.

Hence in the formation of PF6^-, PF5 acts a Lewis acid.

Ammonia is oxidized with air to form nitric oxide in the first step of the production of nitric acid. Two principal gas-phase reactions occur:

Answers

Answer:

4NH₃(g)  + 5O₂(g)  →  4NO(g)  +  6H₂O

2NO(g) + O₂(g) → 2 NO₂

Explanation:

First of all, we need to consider the reaction for production of ammonia. In this reaction we have as reactants, nitrogen and hydroge.

3H₂ (g) +  N₂(g)  →  2NH₃ (g)

Afterwards, ammonia reacts to oxygen, to produce NO and H₂O

The equation for the process will be:

4NH₃(g)  + 5O₂(g)  →  4NO(g)  +  6H₂O

Then, we take the nitric oxide to make it react, to produce NO₂, in order to produce nitric acid, for the final reaction:

2NO(g) + O₂(g) → 2 NO₂

3NO₂(g) + H₂O(g) → 2 HNO₃ (g) + NO(g)

If a 275 mL gas container had pressure of 732.6 mm Hg at -28°C and the gas was condensed into a liquid with a mass of 1.95 g, what is the molar mass of the gas?

Answers

Answer:

THE MOLAR MASS OF THE GAS IS 147.78 G/MOLE

Explanation:

Using PV = nRT

n = Mass / molar mass

P = 732.6 mmHg = 1 atm = 760 mmHg

So therefore 732.6 mmHg will be equal to 732.6 / 760 = 0.964 atm

P = 0.964 atm

V = 275 mL = 275 *10 ^-3 L

R = 0.082 Latm/ mol K

T = -28 C = 273 - 28 K = 245 K

mass =  1.95 g

molar mass = unknown

Having known the other variables in the formula, the molar mass of the gas can be obtained.

PV = m R T/ molar mass

Molar mass = m RT / PV

Molar mass = 1.95 * 0.082 * 245 / 0.964 * 275 *10^-3

Molar mass = 39.1755 / 265.1 *10^-3

Molar mass = 39.1755 / 0.2651

Molar mass = 147.78 g/mol

The molar mass of the gas is 147.78 g/mol

1. The following thermochemical equation is for the reaction of water(l) to form hydrogen(g) and oxygen(g). 2H2O(l)2H2(g) + O2(g) H = 572 kJ How many grams of H2O(l) would be made to react if 110 kJ of energy were provided? _____ grams
2. The following thermochemical equation is for the reaction of carbon monoxide(g) with hydrogen(g) to form methane(g) and water(g). CO(g) + 3H2(g) CH4(g) + H2O(g) H = -206 kJ When 6.27 grams of carbon monoxide(g) react with excess hydrogen(g),_____ kJ of energy are ____ a.evolved b.absorbed

Answers

Answer:

1. 6.92 g of H2O

2i. - 46 KJ of energy.

ii. Option A. Evolved.

Explanation:

1. Determination of the mass of H2O that would be made to react if 110 kJ of energy were provided.

This can be obtained as follow:

The equation for the reaction is given below

2H2O(l) —> 2H2(g) + O2(g) H = 572 kJ

Next, we shall determine the mass of H2O required to produce 572 kJ from the balanced equation.

Molar mass of H2O = (2x1) + 16 = 18 g/mol

Mass of H2O from the balanced equation = 2 x 18 = 36 g

From the balanced equation above, 36 g of H2O reacted to produce 572 kJ of energy.

Finally, we shall determine the mass of water (H2O) needed to produce 110 kJ of energy.

This is illustrated below:

From the balanced equation above, 36 g of H2O reacted to produce 572 kJ of energy.

Therefore, Xg of H2O will react to 110 kJ of energy i.e

Xg of H2O = (36 x 110)/572

Xg of H2O = 6.92 g

Therefore, 6.92 g of H2O is needed to react in order to produce 110 KJ of energy.

2i. Determination of the energy.

The balanced equation for the reaction is given below:

CO(g) + 3H2(g) —> CH4(g) + H2O(g) H = -206 kJ

Next, we shall determine the mass of CO that reacted to produce -206 kJ of energy from the balanced equation.

This is illustrated below:

Molar mass of CO = 12 + 16 = 28 g/mol

Mass of CO from the balanced equation = 1 x 28 = 28 g

From the balanced equation above,

28 g of CO reacted to produce -206 kJ of energy.

Finally, we shall determine the amount of energy produced by reacting 6.27 g of CO. This is illustrated below:

From the balanced equation above,

28 g of CO reacted to produce -206 kJ of energy.

Therefore, 6.27 g of CO will react to produce = (6.27 x -206)/28 = - 46 KJ of energy.

Therefore, - 46 KJ of energy were produced from the reaction.

2ii. Since the energy obtained is negative, it means heat has been given off to the surroundings.

Therefore, the heat is evolved.

Aspirin (C9H8O4) is produced by the reaction of salicylic acid (C7H6O3, Molar mass = 138.1 g/mol) and acetic anhydride (C4H6O3, Molar mass = 102.1 g/mol) based on the BALANCED equation : C7H6O3(s) + C4H6O3(l ) → C9H8O4(s) + C2H4O2( l) If 63.07 grams of aspirin (Molar mass = 180.2 g/mol) was collected from an experiment when 138.1 grams C7H6O3 reacted with excess C4H6O3, what was the percent yield?

Answers

Answer:

35%

Explanation:

Percentage yield = actual yield / theoretical yield × 100.

Given:

Actual yield = 63.07g

Theoretical yield = ?

Mole ratio of C7H6O3 to C4H6O3 = 1 : 1

1 mole of C7H6O3 - 138.1g

Which implies that only 1 mole s[tex]\frac{63.07}{180.2} * 100[/tex]hould be used up in the reaction, yielding 180.2 g of C9H8O4. ⇒ Theoretical yield = 180.2g

∴ % Yield = [tex]\frac{63.07}{180.2} * 100[/tex]

= 35% yield.

Let me know if you found this easy to understand.

The heat of vaporization delta Hv of dichloromethane (Ch2CL2) is 28.0 kJ/mol . Calculate the change in entropy delta S when 473 g of dichloromethane boils at 39.8 degree.

Answers

Answer:

16 J/K.mol

Explanation:

From the question,

ΔS = ΔH/T............... Equation 1

Where ΔH = Heat change, T = Temperature

But,

ΔH = n(Hv).................. Equation 2

Where n = number of  mole, Hv = heat of vaporization.

Given: Hv = 28.0 kJ/mol, n = 473/85 = 5.59 mole.

Substitute these values into equation 2

ΔH = 28/5.59

ΔH = 5.01 kJ.

Also: T = 273+39.8 = 312.8 J

Substitute into equation 1

ΔS = 5.01/312.8

ΔS = 0.016 kJ/K

ΔS = 16 J/K.mol

What is the balanced form of the chemical equation shown below?
Ca(OH)2(aq) + Na2CO3(aq) → CaCO3(s) + NaOH(aq)

Answers

Answer:

D

Explanation:

Double Displacement reaction

Both sides are balanced with option D

The balanced form of the chemical equation shown below is [tex]\rm Ca(OH)_2(aq) + Na_2CO_3(aq) \rightarrow CaCO_3(s) + 2NaOH(aq).[/tex] The correct option is D.

What is a balanced equation?

A balanced equation is where the reactant and the product have the number of moles of elements. According to the law, the reaction, and the product have the same number of moles after the reaction, so balancing an equation is important.

To balance an equation, it is significant to see the number of moles of reactant and the same number of moles is in the product side. Here the moles of sodium has to be balanced.

Thus, the correct option is D, [tex]\rm Ca(OH)_2(aq) + Na_2CO_3(aq) \rightarrow CaCO_3(s) + 2NaOH(aq).[/tex]

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Which statement is true according to the kinetic theory? Will mark brainliest

Answers

Answer:

[tex]\boxed{\sf Option \ E}[/tex]

Explanation:

All the gases at the same temperature and mass have the same average kinetic energy.

If the masses were different, then the different gases will have different velocities. If the temperature was higher then there would be a greater motion, if the temperature was lower, then there would be less motion.

Answer:

option E

Explanation:

Which of these groups of elements show the least electronegativity?

Answers

Explanation:

On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group. As a result, the most electronegative elements are found on the top right of the periodic table, while the least electronegative elements are found on the bottom left. The answer is alkali metals.

What do chemists use percent yield calculations for in the real world?
A. To balance the reaction equation.
B. To determine how much product they will need.
C. To determine how efficient reactions are.
D. To determine how much reactant they need.

Answers

Answer:

C. To determine how efficient reactions are.

D. To determine how much reactant they need.

Explanation:

When you are doing a reaction, you are hoping for a percent yield to close of 100%. You make the reaction and determine how many product you obtain. If you know the percent yield of a reaction you can calculate the amount of reactant you need to obtain a determined amount of product.

Having this in mind:

A. To balance the reaction equation.  false. To calculate percent yield you need to balance the reaction before. You don't use percent yield to balance the reaction

B. To determine how much product they will need.  false. You determine how much product you obtain after the reaction. How much product you need is independent of percent yield

C. To determine how efficient reactions are.  true. A way to determine efficience of a reaction is with percent yield. An efficient reaction has a high percent yield.

D. To determine how much reactant they need. true. If you know percent yield of a reaction you can know how many reactant you must add to obtain  the amount of product you want.

Considering that catalysts are not consumed in a reaction, how do you think increasing the amount of catalyst would affect the reaction rate for the decomposition of hydrogen peroxide?

a. increase
b. decrease
c. no effect

Answers

Answer:

a. increase

Explanation:

Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst, which is not consumed in the catalyzed reaction.

By default, catalysts exists to speed up the rate of reactions. Increasing the amount of catalysts means that there would be an increase in the rate of reaction. The correct option is A.

Calculate the mass percent of .485g of H, which reacts with O to form 2.32g H2O?

Answers

Answer:

53.1% of hydrogen reacts

Explanation:

The mixture of 2 atoms of H with 1 atom of O produce 1 molecule of H₂.

The mass of hydrogen in 2.32g of H₂O could be obtained using molar mass of H₂O (18.01g/mol) and molar mass of hydrogen (1.01g/mol) as follows:

Moles H₂O: 2.32g H₂O × (1mole / 18.01g) = 0.1288 moles of water

1 mole of H₂O contains 2 moles of H, moles of hydrogen in 0.1288 moles of water are:

0.1288 moles H₂O × (2 moles H / 1 mole H₂O) = 0.2576 moles of H

In mass:

0.2576 moles H × (1.01g/ mol H) = 0.260g H you have in the formed water

As before reaction you had 0.485g of H and just 0.260g reacted, mass percent is:

(Mass that reacts / Mass added) × 100

(0.260g / 0.485g) × 100 =

53.1% of hydrogen reacts

Draw the Lewis structure of ethyne (C₂H₂) and then choose the appropriate pair of molecular geometries of the two central atoms. Your answer choice is independent of the orientation of your drawn structure.
A) linear / linear
B) trigonal/pyramidal
C) pyramidal/trigonal
D) trigonal pyramidal/trigonal pyramidal
E) planar / linear

Answers

Answer:

A) linear / linear

Explanation:

In this case, we have a triple bond beetween the atoms (See figure 1). If we have this triple bond we will have an Sp hybridization (in both carbons). We have to remember the relationship between the geometry and the hybridization:

-) Sp3 = Tetrahedral

-) Sp2 = Trigonal

-) Sp = Linear

Due to the hybridization, we will have a linear structure between the atoms. The angle between the atoms is 180º (See figure 2).

So, if we have a hybridization Sp for both carbons, we will have a linear geometry in each carbon. Therefore, the answer is A.

Determine the half-life of a nuclide that loses 38.0% of its mass in 407 hours. Determine the half-life of a nuclide that loses 38.0% of its mass in 407 hours. 204 hours 568 hour 590 hours 291 hours 281 hours

Answers

Answer:

Use 62% - the equation is for the amount present at a given time. 0.62 = (1) e-kt -> ln(0.62)=-kt -> k = -ln(0.62)/t. I get k = .00117 hr-1 t(half) = 0.693/k = 590 hr.

HOPE THIS HELPS AND PLSSS MARK AS BRAINLIEST AND THNXX :)

The half-life is the time at which the substance's concentration is reduced by half of its initial amount. The half-life of a nuclide that lost its 38.0% mass is 590 hr. Thus, option C is correct.

What is half-life?

Half-life is the time required by a substance to get reduced to half of its initial concentration. The half-life of the substance can be determined by the rate constant.

Given,

The initial quantity of substance (A₀) = 100

Remaining quantity (At) = 10 - 38 = 62

Time elapse (t) = 407 hours

The rate constant (k) is calculated as:

ln (At ÷ A₀) = - kt

ln (62 ÷ 100) ÷ 407 hour = - k

-0.47803580094 ÷ 407 = - k

k = 0.00117453513

Now, half-life from rate constant (k) is calculated as:

[tex]\rm t ^{\frac{1}{2}}[/tex] = 0.693 ÷ k

[tex]\rm t ^{\frac{1}{2}}[/tex] = 0.693 ÷ 0.00117453513

[tex]\rm t ^{\frac{1}{2}}[/tex] = 590 hours

Therefore, option C. 590 hours is the half-life of the substance.

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Given a fixed amount of gas help at a constant pressure, calculate the temperature to which the gas would have to be changed if a 1.75 L sample at 23.0*C were to have a final volume of 3.50 L.
A. 46.0*C
B. 89.5*C
C. 169*C
D. 319*C
E. 592*C

Answers

Answer:

592 K or 319° C

Explanation:

From the statement of Charles law we know that the volume of a given mass of gas is directly proportional to its absolute temperature at constant pressure. Thus;

V1/T1= V2/T2

Initial volume V1 = 1.75 L

Initial temperature T1= 23.0 +273 = 296 K

Final volume V2= 3.50 L

Final temperature T2 = the unknown

T2= V2T1/V1= 3.50 × 296 / 1.75

T2 = 592 K or 319° C

The ionization constant of lactic acid ch3ch(oh) co2h am acid found in the blood after strenuous exercise is 1.36×10^-4 If 20.0g of latic acid is used to make a solution with a volume of 1.00l what is the concentration of hydronium ion in the solution

Answers

Answer:

Explanation:

CH₃CHOHCOOH    ⇄    CH₃CHOHCOO⁻   +    H⁺

ionisation constant = 1.36 x 10⁻⁴ .

molecular weight of lactic acid = 90 g

moles of acid used = 20 / 90

= .2222

it is dissolved in one litre so molar concentration of lactic acid formed

C = .2222M

Let n be the fraction of moles ionised  

CH₃CHOHCOOH    ⇄    CH₃CHOHCOO⁻   +    H⁺

C  - nC                                          nC                  nC

By definition of ionisation constant Ka

Ka = nC x nC / C - nC

= n²C ( neglecting n in the denominator )

n² x .2222 = 1.36 x 10⁻⁴

n = 2.47  x 10⁻²

nC = 2.47  x 10⁻² x .2222

= 5.5 x 10⁻³

So concentration of hydrogen or hydronium ion = 5.5  x 10⁻³ g ion per litre .

The concentration of hydrogen or hydronium ion = 5.5  x 10⁻³ g ion per liter .

Ionization of lactic acid can be represented as:

CH₃CHOHCOOH⇄ CH₃CHOHCOO⁻  + H⁺

Given:

ionization constant = 1.36 x 10⁻⁴

mass= 20.0 g

Now, Molecular weight of lactic acid = 90 g

[tex]\text{Number of moles}=\frac{20}{90} =0.22mol[/tex]

It is dissolved in 1.00L so molar concentration of lactic acid formed will be

C = 0.22M

Consider "n" to be the fraction of moles ionized  

CH₃CHOHCOOH    ⇄    CH₃CHOHCOO⁻   +    H⁺

C  - nC                                          nC                  nC

By definition of ionization constant Ka

[tex]K_a =\frac{nC*nC}{C-nC}[/tex]

[tex]K_a= n^2C[/tex] ( neglecting n in the denominator )

On substituting the values we will get:

[tex]n^2 *0.22 = 1.36 *10^{-4}\\\\n = 2.47 * 10^{-2}[/tex]

To find the concentration of hydronium ion in the solution,

[tex]nC = 2.47 *10^{-2} *0.22\\\\nC= 5.5 * 10^{-3}[/tex]

So, concentration of hydrogen or hydronium ion = 5.5  x 10⁻³ g ion per liter.  

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What is the purpose of reacting 2.0mL of HNO3 with 2.0 mL of H2SO4 in a separate test tube, prior to adding it to the solution containing the substrate

Answers

The question is incomplete, the complete question is;

What is the purpose of reacting 2.0mL of HNO3 with 2.0 mL of H2SO4 in a separate test tube, prior to adding it to the solution containing the substrate? more than one answer is possible

A) The release of a water molecule that acts as an electrophile in the reaction with methyl benzoate.

B) The formation of nitronium ion, which acts an electrophile in the reaction with methylbenzoate.

C)The formation of bisulfate (hydrogen sulfate), which acts as an electrophile in the reaction with methylbenzoate.

D)The release of a water molecule that acts as a nucleophile in the reaction with methyl benzoate.

Answer:

B) The formation of nitronium ion, which acts an electrophile in the reaction with methylbenzoate.

Explanation:

The benzene ring is known to be stable hence it can only undergo a substitution reaction with the aromatic ring still intact. When the substitution reaction involves an electrophile we refer to the process as electrophillic aromatic substitution. Electrophilic aromatic substitution is a useful synthetic route for many organic compounds.

In the electrophilic substitution of methyl benzoate using the 1:1 volume ratio mixture of H2SO4/HNO3, the nitronium ion (NO2+) is the electrophile generated in the test tube. It is this NO2+ that now reacts with the methyl benzoate to yield the reaction product.

A sample of an unknown gas effuses in 11.1 min. An equal volume of H2 in the same apparatus at the same temperature and pressure effuses in 2.42 min. What is the molar mass of the unknown gas

Answers

Answer:

Molar mass of the gas is 0.0961 g/mol

Explanation:

The effusion rate of an unknown gas = 11.1 min

rate of [tex]H_{2}[/tex] effusion = 2.42 min

molar mass of hydrogen = 1 x 2 = 2 g/m

molar mas of unknown gas = ?

From Graham's law of diffusion and effusion, the rate of effusion and diffusion is inversely proportional to the square root of its molar mass.

from

[tex]\frac{R_{g} }{R_{h} }[/tex] = [tex]\sqrt{\frac{M_{h} }{M_{g} } }[/tex]

where

[tex]R_{h}[/tex] = rate of effusion of hydrogen gas

[tex]R_{g}[/tex] = rate of effusion of unknown gas

[tex]M_{h}[/tex] = molar mass of H2 gas

[tex]M_{g}[/tex] = molar mass of unknown gas

substituting values, we have

[tex]\frac{11.1 }{2.42 }[/tex] = [tex]\sqrt{\frac{2 }{M_{g} } }[/tex]

4.587 = [tex]\sqrt{\frac{2 }{M_{g} } }[/tex]

[tex]\sqrt{M_{g} }[/tex] = [tex]\sqrt{2}[/tex]/4.587

[tex]\sqrt{M_{g} }[/tex] = 0.31

[tex]M_{g}[/tex] = [tex]0.31^{2}[/tex] = 0.0961 g/mol

The molar mass of the unknown gas will be "0.0961 g/mol".

Given:

Effusion rate of unknown gas,

[tex]R_g = 11.1 \ min[/tex]

Effusion rate of [tex]H_2[/tex],

[tex]R_h = 2.42 \ min[/tex]

Molar mass of hydrogen,

[tex]M_h = 1\times 2[/tex]

              [tex]= 2 \ g/m[/tex]

According to the Graham's law, we get

→    [tex]\frac{R_g}{R_h} = \sqrt{\frac{M_h}{M_g} }[/tex]

By substituting the values, we get

→   [tex]\frac{11.1}{2.42} = \sqrt{\frac{2}{M_g} }[/tex]

→ [tex]4.587=\sqrt{\frac{2}{M_g} }[/tex]

→ [tex]\sqrt{M_g} = \sqrt{\frac{2}{4.587} }[/tex]

   [tex]\sqrt{M_g} = 0.31[/tex]

       [tex]M_g = 0.0961 \ g/mol[/tex]

Thus the above solution is right.          

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What's the difference between velocity time graph and distance time graph​

Answers

Explanation:

Hi there!

I attached a photo of a unit summary that states the difference between s-t and v-t graph.

Hope this helps ;) ❤❤❤

Using the bond energy data from your text (or the internet), determine (show calculations for) the approximate enthalpy change , ∆H, for each of the following reactions: (a) Cl2 (g) + 3F2 (g) ⟶ 2ClF3 (g)

Answers

Answer:

∆H=  438 KJ/mol

Explanation:

First, we have to find the energy bond values for each compound:

-) Cl-Cl = 243 KJ/mol

-) F-F = 159 KJ/mol

-) F-Cl = 193 KJ/mol

If we check the reaction we can calculate the number of bonds:

[tex]Cl_2_(_g_)~+~3F_2_(_g_)~->~2ClF_3_(_g_)[/tex]

In total we will have:

-) Cl-Cl = 1

-) F-F = 3

-) F-Cl = 6

With this in mind. we can calculate the total energy for each bond:

-) Cl-Cl = (1*243 KJ/mol) = 243 KJ/mol

-) F-F = (3*159 KJ/mol) = 477 KJ/mol

-) F-Cl = (6*193 KJ/mol) = 1158 KJ/mol

Now, we can calculate the total energy of the products and the reagents:

Reagents = 243 KJ/mol + 477 KJ/mol = 720 KJ/mol

Products = 1158 KJ/mol

Finally, to calculate the total enthalpy change we have to do a subtraction between products and reagents:

∆H= 1158 KJ/mol-720 KJ/mol = 438 KJ/mol

I hope it helps!

The approximate enthalpy change is:

∆H=  438 KJ/mol

Calculation for enthalpy change:

First, we have to find the energy bond values for each compound:

Cl-Cl = 243 KJ/mol

F-F = 159 KJ/mol

F-Cl = 193 KJ/mol

Balanced chemical reaction:

Cl₂ (g) + 3F₂ (g) ⟶ 2ClF₃ (g)

Total number of bond for each:

Cl-Cl = 1

F-F = 3

F-Cl = 6

Total bond energy will be:

Cl-Cl = (1*243 KJ/mol) = 243 KJ/mol

F-F = (3*159 KJ/mol) = 477 KJ/mol

F-Cl = (6*193 KJ/mol) = 1158 KJ/mol

Now, we can calculate the total energy of the products and the reactants:

Reactants = 243 KJ/mol + 477 KJ/mol = 720 KJ/mol

Products = 1158 KJ/mol

Finally, to calculate the total enthalpy change we have to do a subtraction between products and reagents:

∆H= 1158 KJ/mol-720 KJ/mol = 438 KJ/mol

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Solid iron(II) oxide reacts with oxygen gas to produce solid iron(III) oxide. Balance the equation for this reaction (in lowest multiple integers). Write the unbalanced equation for this reaction.

Answers

Answer

Hello

I think the reaction is like this FeO+OFe²O³

And the balance reaction is 2Fe+OFe²O³

Explanation:

At first we should find sth that has more atoms than the other then for example we realized that we have two atoms of Fe in Fe²O³ then put 2 before FeO and now we have 2 atoms of Fe in right side and 2 atoms of Fe in left then Oxygen in FeO change to 2 atoms of Oxygen and we have an other one in right side that they become 3 atoms of Oxygen and now we have 3 atoms of Oxygen in both right and left side.

Finally our reaction balanced.

Good luck

Need help please! Theres three parts to this that I don't understand at all

Answers

Answer:

Chemical reaction B governs the process

Explanation:

The first part of the question asks to convert the mass of the calcium carbonate given to number of moles.

Mathematically;

Number of moles = mass/molar mass

Molar mass of CaCO3 = 100 g/mol

So the number of moles of CaCO3 will be 2.49/100 = 0.0249 moles

The second part of the question asks to convert the mass of carbon iv oxide to moles of carbon iv oxide

Mathematically;

That is same as ;

Number of moles = mass/molar mass

molar mass of CO2 is 44 g/mol

Number of moles of CO2 = 1.13/44 = 0.0256 moles

Now, if we compare the values of these number of moles, we can see that there are almost equal.

What this means is that the number of moles of calcium carbonate reacted is equal to the number of moles of carbon iv oxide produced.

So what we conclude here is that we have an equal mole ratio between the two compounds.

So the reaction that would be the correct answer will present equal number of moles of carbon iv oxide and calcium carbonate

Thus, we can see that reaction B is the one that governs this process as it is the only reaction out of the three options that present the two compounds with equal number of moles.

Zinc bromide is considered which of the following?

A) molecular compound

B) atomic element

C) molecular element

D) ionic compound

Answers

Answer:

D

Explanation:

soluble in water and acidic

What amounts of sodium benzoate would be required to prepare 2.5L of 0.35M benzoic buffer solution with a pH of 6.10? Ka of benzoic acid = 6.5 x 10-5 MW benzoic acid, HC7H5O2, is 122.01 MW sodium benzoate, NaC7H5O2, is 144.01

Answers

Answer:

Benzoic acid: 1.288g

Sodium benzoate: 124.48g

Explanation:

Benzoic acid, HC7H5O2 is in equilibrium with its conjugate base, C7H5O2⁻ producing a buffer. The pH of the buffer can be determined following H-H equation:

pH = pKa + log [C7H5O2⁻] / [HC7H5O2] (1)

Where pH is desire pH = 6.10 pKa is -log Ka = 4.187 and [] are molar concentrations of the buffer.

As you want to prepare 2.5L of a 0.35M of buffer, moles of buffer are:

2.5L ₓ (0.35mol / L) = 0.875moles of buffer.

And you can write:

0.875 moles = [C7H5O2⁻] + [HC7H5O2] (2)

Replacing (2) in (1)

pH = pKa + log [C7H5O2⁻] / [HC7H5O2]

6.10 = 4.187 + log [C7H5O2⁻] / [HC7H5O2]

1.913 =  log [C7H5O2⁻] / [HC7H5O2]

81.846 = 0.875mol - [HC7H5O2] / [HC7H5O2]

81.846 [HC7H5O2] = 0.875mol - [HC7H5O2]

82.846 [HC7H5O2] = 0.875mol

[HC7H5O2] = 0.01056 moles

And moles of the benzoate, [C7H5O2⁻]:

[C7H5O2⁻] = 0.875mol - 0.01056mol =

[C7H5O2⁻] = 0.8644mol

Using molar mass of benzoic acid and sodium benzoate, amount of each compound you must add to prepare 2.5L of the buffer are:

Benzoic acid: 0.01056mol ₓ (122.01g/mol) = 1.288g

Sodium benzoate: 0.8644mol ₓ (144.01g/mol) = 124.482g

Determine the pH during the titration of 25.5 mL of 0.276 M hydroiodic acid by 0.105 M barium hydroxide at the following points: (1) Before the addition of any barium hydroxide .55 (2) After the addition of 16.7 mL of barium hydroxide (3) At the equivalence point (4) After adding 40.7 mL of barium hydroxide

Answers

Answer:

1) before the addition of barium hydroxide

pH = -log[H⁺] = -log (0.276) = 0.559≈0.56

2)after the addition of barium hydroxide

pH = -log [H⁺] = -log(0.0857) = 1.067

3)at equivalent point, the solution will be neutral

pH = 7.0

4) after adding 40.7mL barium hydroxide

Explanation:

equation of reaction

2HCl(aq) + Ba(OH)₂(aq) ------->BaCl₂(aq) + 2H₂O(l)

1) Before the addition of barium hydroxide

concentration of HBr = 0.276M

[H⁺] = 0.276M

pH = -log[H⁺] = -log (0.276) = 0.559≈0.56

2) After adding 16.7mL barium hydroxide

moles of [OH⁻] = 16.7mL × 0.105 × 2

=3.507m mol = 3.507 × 10³mol

moles  of [H⁺] = 25.5mL × 0.276M

=7.038m mol = 7.038 × 10³mol

moles of  [H⁺] remaining = (7.038 - 3.421)m mol

= 3.617m mol = 3.617 × 10³mol

[H⁺]= [tex]\frac{3.617}{25.5 + 16.7}[/tex] = 0.0857

pH = -log [H⁺] = -log(0.0857) = 1.067

3) At equivalent point, the solution will be neutral

pH = 7.0

4) After adding 40.7mL barium hydroxide

moles of [OH⁻] = 40.7mL × 0.105M × 2

=8.547

moles of [OH⁻] remaining = 8.547 - 7.038

= 1.509m mol = 1.509 × 10³mol

pOH= -log[OH⁻]= 2.82

pH = 14 - 2.82 = 11.18

There are parts of a standing wave that do not move at all. These parts are called ___________.

Answers

Answer:

They are called nodes.

Explanation:

Answer:

i guess this is the ans nodes

hope this helps

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Determine the volume occupied by 10 mol of helium at
27 ° C and 82 atm

Answers

Answer:

3.00 L

Explanation:

PV = nRT

(82 atm × 101325 Pa/atm) V = (10 mol) (8.314 J/mol/K) (27 + 273) K

V = 0.00300 m³

V = 3.00 L

Medical implants and high-quality jewelry items for body piercings are frequently made of a material known as G23Ti or surgical-grade titanium. The percent composition of the material is 64.39% titanium, 24.19% aluminum, and 11.42% vanadium. What is the empirical formula for surgical-grade titanium

Answers

Answer:

The Empirical Formular is given as; Ti₆Al₄V

Explanation:

The percent composition of the material is 64.39% titanium, 24.19% aluminum, and 11.42% vanadium.

Elements                        Titanium            Aluminium        Vanadium

Percentage                    64.39                 24.19                   11.42

Divide all through by their molar mass

                                     64.39 / 47.87      24.19 / 27               11.42 / 50.94

                                       =  1.345                = 0.896                 = 0.224

Divide all though  by the smallest number (0.224)

                                     1.345 / 0.224        0.896 / 0.224       0.224 / 0.224

                                     = 6                         = 4                             = 1

The Empirical Formular is given as; Ti₆Al₄V

Using the stepwise procedure for obtaining the empirical formula of a compound, the empirical formula is [tex] T_{6}Al_{4}V[/tex]

Titanium :

Percentage composition = 64.39%Molar mass = 47.87

Divide by Molar mass : = 64.39/47.87 = 1.345

Aluminum :

Percentage composition = 24.19%Molar mass = 27

Divide by Molar mass : = 24.19/27 = 0.896

Vanadium :

Percentage composition = 11.42%Molar mass = 50.94%

Divide by Molar mass : = 11.42/50.94 = 0.224

Divide by the smallest :

Titanium = 1.345 / 0.224 = 6.00

Aluminum = 0.896 / 0.224 = 4

Vanadium = 0.224 / 0.224 = 1

Hence, the empirical formula is [tex] T_{6}Al_{4}V[/tex]

Learn more : https://brainly.com/question/17091379

A pharmaceutical company is making a large volume of nitrous oxide (NO). They predict they will be able to make a maximum amount of 4860 grams with the materials they have in stock. From the previous 10 volumes they have made, they know that the percent yield of this reaction is fairly low at 47%. How much will the actual yield be?

Answers

Answer:

2284.2 g.

Explanation:

The following data were obtained from the question:

Percentage yield = 47%

Theoretical yield = 4860 g

Actual yield =?

The percentage yield is simply defined as the ratio of actual yield to the theoretical yield multiplied by 100. Mathematically, it is expressed as:

Percentage yield = Actual yield /Theoretical yield x 100

With the above formula, we can obtain the actual yield as follow:

Percentage yield = Actual yield /Theoretical yield x 100

47% = Actual yield /4860

Cross multiply

Actual yield = 47% × 4860

Actual yield = 47/100 x 4860

Actual yield = 2284.2 g

Therefore, the actual yield is 2284.2 g.

At 850 K, the equilibrium constant for the reaction
2SO2(g)+O2(g)↽−−⇀2SO3(g)
is Kc=15. If the given concentrations of the three gases are mixed, predict in which direction the net reaction will proceed toward equilibrium.
Left No net reaction Right

Answers

Answer:

Answers are in the explanation.

Explanation:

Given concentrations are:

SO₂ = 0.20M O₂ = 0.60M SO₃ = 0.60MSO₂ = 0.14M O₂ = 0.10M SO₃ = 0.40M And SO₂ = 0.90M O₂ = 0.50M SO₃ = 0.10M

In the reaction:

2SO₂(g) + O₂(g) ⇄ 2SO₃(g)

Kc is defined as:

Kc = 15 = [SO₃]² / [O₂] [SO₂]²

Where concentrations of each species are equilbrium concentrations.

Also, you can define Q (Reaction quotient) as:

Q = [SO₃]² / [O₂] [SO₂]²

Where concentrations of each species are ACTUAL concentrations.

If Q > Kc, the reaction will shift to the left until Q = Kc;

If Q < Kc, the reaction will shift to the right until Q = Kc

If Q = Kc, there is no net reaction because reaction would be en equilibrium.

Replacing with given concentrations:

Q = [0.60M]² / [0.60M] [0.20M]² = 15; Q = Kc → No net reactionQ = [0.40M]² / [0.10M] [0.14M]² = 82; Q > Kc, → Reaction will shift to the leftQ = [0.10M]² / [0.50M] [0.90M]² = 0.015; Q < Kc → Reaction will shift to the right

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