Answer:
2NaOH(s) → Na₂O(s) + H₂O(g)
Hope that helps.
A chemist adds of a mercury(I) chloride solution to a reaction flask. Calculate the micromoles of mercury(I) chloride the chemist has added to the flask.
Answer:
3.383x10⁻³ micromoles of HgCl
Explanation:
The chemist adds 170mL of a 1.99x10⁻⁵mmol/L Mercury (I) chloride, HgCl.
The solution contains 1.99x10⁻⁵milimoles of HgCl in 1L. That means in 170mL = 0.170L there are:
0.170L × (1.99x10⁻⁵milimoles HgCl / L) = 3.383x10⁻⁶ milimoles of HgCl.
Now, in 1milimole you have 1000 micromoles. That means in 3.383x10⁻⁶ milimoles of HgCl you have:
3.383x10⁻⁶ milimoles of HgCl ₓ (1000micromoles / 1milimole) =
3.383x10⁻³ micromoles of HgClDo you expect the compound Na4S to be a stable sulfur compound? Explain why or why not. Select the correct answer below: A. Yes, because sulfur is significantly more electronegative than sodium, so it can ionize sodium. B. Yes, because sodium is significantly more electronegative than sulfur, so it can ionize sulfur. C. No, because sulfur does not typically form negative ions or oxidation states less than 2−. The binary compound formed by sulfur and sodium is Na2S. D. No, because elemental sulfur is not a strong enough oxidation agent to oxidize sodium.
Answer:
No, because sulfur does not typically form negative ions or oxidation states less than 2−. The binary compound formed by sulfur and sodium is Na2S
Explanation:
Sulphur is a member of group 16. The oxidation states expected for sulphur in group 16 are -1, -2, +1, +2,+3,+4,+5 or +6. The elements of group 16 usually form negative ions with oxidation number of -2. They do not typically form negative ions with oxidation state less than -2.
The implication of this is that we actually do not expect the existence of a compound in which sulphur forms an S^4- anion. In reality, such an anion does not exist. Rather a binary compound of sulphur and sodium will have the formula Na2S because it contains the S^2- anion.
30. What is the Bronsted base of H2PO4- + OH- ⟶HPO42- + H2O?
Answer:
OH⁻ is the Bronsted-Lowry base.
Explanation:
A Bronsted-Lowry base is a substance that accepts protons. In the chemical equation, OH⁻ accepts a proton from H₂PO₄⁻ to become H₂O. H₂PO₄⁻ would be a Bronsted-Lowry acid because it donates a proton to OH⁻ and becomes HPO₄²⁻.
Hope that helps.
Which of the following properties should carbon (C) have based on its position on
the periodic table?
A. Shiny
B. Dense
C. Malleable
D. Poor conductor
Answer:
D- poor conductor
Explanation:
metallic properties decrease as we go on the right of the periodic table. Carbon is a non metal hence it is dull and a poor conductor.
it has a low density and is ductile.
Answer: Poor conductor
Explanation:
Suppose of nickel(II) iodide is dissolved in of a aqueous solution of potassium carbonate. Calculate the final molarity of nickel(II) cation in the solution. You can assume the volume of the solution doesn't change when the nickel(II) iodide is dissolved in it. Round your answer to significant digits.
Answer:
0.619 M to 3 significant figures.
Explanation:
1 mole of [tex]NiI_{2}[/tex] - 312.5 g
? mole of [tex]NiI_{2}[/tex] - 2.9 g
= 2.9/312.5
= 0.0928 moles.
Concentration = no. of moles/vol in litres = [tex]\frac{0.0928}{0.150L}[/tex]
= 0.619 M
Consider the following reaction (X = Cl or Br) which statement s is are correct?
CH3CH2CH3 + X2---------CH3CHCH3--X + CH3CH2CH2--X
i. statistically the 1 halopropane should be the major isomer
ii. the 2 halopropane to 1 halopropane ratio is largest when X = Br
iii. the 2 halopropane to 1 halopropane ratio is largest when X = Cl
A. only Il
B. only Ill
C. I and II
D. I and III
A.S OLOS kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkll
To determine the concentration of chloride ion (Cl-) in a 100 mL sample of ground water, a chemist adds a large enough volume of AgNO3 solution to precipitate all Cl- as AgCl. The mass of the resulting precipitate is 93.9 mg. What is the chloride ion concentration in milligrams of chloride per liter of ground water
Answer:
[tex][Cl^-]=232.3\frac{mgCl^-}{L}[/tex]
Explanation:
Hello,
In this case, we can represent the chemical reaction as:
[tex]Cl^-(aq)+AgNO_3(aq)\rightarrow AgCl(s)+NO_3^-(aq)[/tex]
In such a way, since the mass of the obtained silver chloride is 93.9 mg, we can compute the chloride ions in the ground water by using the following stoichiometric procedure whereas the molar mass of chloride ions and silver chloride are 35.45 g/mol and 143.32 g/mol respectively:
[tex]m_{Cl^-}=93.3mgAgCl*\frac{1mmolAgCl}{143.32mgAgCl}*\frac{1mmolCl^-}{1mmolAgCl} *\frac{35.45mgCl^-}{1mmolCl^-} =23.23mgCl^-[/tex]
Finally, for the given volume of water in liters (0.100L), we compute the required concentration:
[tex][Cl^-]=\frac{23.2mgCl^-}{0.100L}\\[/tex]
[tex][Cl^-]=232.3\frac{mgCl^-}{L}[/tex]
Best regards.
The concentration of chloride ions in the groundwater sample is 230 mg/L.
Calculation of chloride ion concentration:Based on the given information,
The mass of the resulting precipitate, that is, AgCl is 93.9 mg or 0.0939 g. The molar mass of AgCl is 143.2 g/mol.Now the number of moles of AgCl precipitate can be calculated as,
n = Given mass/Molar mass
Now putting the values we get,
[tex]n = \frac{0.939 g}{143.32 g/mol} \\n = 6.5 * 10^{-4}[/tex]
Thus, 6.5 × 10⁻⁴ moles of AgCl comprises 6.5 × 10⁻⁴ chloride ions. Therefore, 6.5 × 10⁻⁴ of chloride ions are present in the sample of 100 ml.
Now the molar mass of chloride ion is 35.453 g/mol, the mass of chloride ion will be,
Mass = Mole × Molar mass
Mass = 6.5 × 10⁻⁴ moles × 35.453 g/mol
Mass = 0.0230 g or 23 mg
The volume of the groundwater sample is 100 ml or 0.1000 L.
Now the concentration of the chloride ions in the sample given is,
C = 23 mg/0.1000 L
C = 230 mg/L
Thus, the concentration of chloride ions in the groundwater sample is 230 grams per liter.
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The reaction, 2 SO3(g) <--> 2 SO2(g) + O2(g) is endothermic. Predict what will happen if the temperature is increased.
Explanation:
This reaction is in equilibrium and would hence obey lechatelier's principle. This principle states that whenever a system at equilibrium undergoes a change, it would react in way so as to annul that change.
Since it is an endothermic reaction, increasing the temperature would cause the reaction to shift towards the right.
This means that it favours product formation and more of the product would be formed.
· A 0.100g sample of Mg when combined with O2 yields 0.166g of Mgo, a
second Mg sample with a mass of 0.144g is also combined with O2. What
mass of MgO is produced from the second sample?
Answer:
[tex]m_{MgO}=0.239gMgO[/tex]
Explanation:
Hello,
In this case, the chemical reaction between magnesium and oxygen to yield magnesium oxide is:
[tex]2Mg+O_2\rightarrow 2MgO[/tex]
In such a way, for 0.144 g of magnesium reacting with sufficient oxygen, the mass of magnesium oxide, whose molar mass is 40.3 g/mol (2:2 mole ratio) turns out:
[tex]m_{MgO}=0.144gMg*\frac{1molMg}{24.3gMg} *\frac{2molMgO}{2molMg}* \frac{40.3gMgO}{1molMgO} \\\\m_{MgO}=0.239gMgO[/tex]
Best regards.
A compound decomposes with a half-life of 8.0 s and the half-life is independent of the concentration. How long does it take for the concentration to decrease to one-ninth of its initial value
Answer:
The concentration takes 25.360 seconds to decrease to one-ninth of its initial value.
Explanation:
The decomposition of the compound has an exponential behavior and process can be represented by this linear first-order differential equation:
[tex]\frac{dc}{dt} = -\frac{1}{\tau}\cdot c(t)[/tex]
Where:
[tex]\tau[/tex] - Time constant, measured in seconds.
[tex]c(t)[/tex] - Concentration of the compound as a function of time.
The solution of the differential equation is:
[tex]c(t) = c_{o} \cdot e^{-\frac{t}{\tau} }[/tex]
Where [tex]c_{o}[/tex] is the initial concentration of the compound.
The time is now cleared in the result obtained previously:
[tex]\ln \frac{c(t)}{c_{o}} = -\frac{t}{\tau}[/tex]
[tex]t = -\tau \cdot \ln \frac{c(t)}{c_{o}}[/tex]
Time constant as a function of half-life is:
[tex]\tau = \frac{t_{1/2}}{\ln 2}[/tex]
Where [tex]t_{1/2}[/tex] is the half-life of the composite decomposition, measured in seconds.
If [tex]t_{1/2} = 8\,s[/tex], then:
[tex]\tau = \frac{8\,s}{\ln 2}[/tex]
[tex]\tau \approx 11.542\,s[/tex]
And lastly, given that [tex]\frac{c(t)}{c_{o}} = \frac{1}{9}[/tex] and [tex]\tau \approx 11.542\,s[/tex], the time taken for the concentration to decrease to one-ninth of its initial value is:
[tex]t = -(11.542\,s)\cdot \ln\frac{1}{9}[/tex]
[tex]t \approx 25.360\,s[/tex]
The concentration takes 25.360 seconds to decrease to one-ninth of its initial value.
If the sugar concentration in a cell is 3% and the concentration in the cell’s environment is 5%, how can the cell obtain more sugar? {Hint: Sugar is polar and does not pass through the cell membrane easily.}
Select one:
a. Sugar can undergo facilitated diffusion through a channel protein, and no energy is required.
b. The cell must use active transport to pump the sugar in. Energy is required.
c. Sugar can diffuse straight through the phospholipid bilayer.
d. The cell CANNOT obtain more sugar. It is doomed.
The cell can obtain more sugar when the sugar undergo facilitated diffusion through a channel protein, and no energy is required.
FACILITATED DIFFUSION:
Facilitated diffusion is the process whereby molecules move across a cell through the help of carrier/channel proteins. Facilitated diffusion is a type of passive transport and hence, does not require energy to occur. This is because movement occurs down a concentration gradient (high to low). According to this question, the sugar concentration in a cell is 3% and the concentration in the cell’s environment is 5%. This means that the sugar can travel down a concentration gradient across the cell membrane. However, because sugar is a polar molecule and does not pass through the cell membrane easily, a carrier proteins is needed to aid its movement. Therefore, the cell can obtain more sugar when the sugar undergo facilitated diffusion through a channel protein, and no energy is required.Learn more at: https://brainly.com/question/18122054?referrer=searchResults
Which characteristic of life best describes the process of photosynthesis?
Answer:
Using energy.
Explanation:
a certain compound was found to contain 54.0 g of carbon and 10.5 grams of hydrogen. its relative molecular mass is 86.0. find the empirical and molecular formulas
Answer:
empirical formula = C3H7
molecular formula = C6H14
The equilibrium constant is given for two of the reactions below. Determine the value of the missing equilibrium constant. A(g) + 2B(g) ↔ AB2(g) Kc = 59 AB2(g) + B(g) ↔ AB3(g) Kc = ? A(g) + 3B(g) ↔ AB3(g) Kc = 478
Answer:
The correct answer is 8.10
Explanation:
Given:
A(g) + 2B(g) ↔ AB₂(g) Kc = 59 ---- Eq. 1
A(g) + 3B(g) ↔ AB₃(g) Kc = 478 ----- Eq. 2
We have to rearrange the chemical equations in order to obtain:
AB₂(g) + B(g) ↔ AB₃(g) Kc = ?
AB₂(g) is a reactant, so we have to use the reverse reaction of Eq. 1, in this case Kc= 1/59. Since AB₃(g) is a product, we use the forward reaction of Eq.2, and the constant is the same: Kc= 478. The following is the sum of rearranged chemical equations, and the compounds in bold and italic are canceled:
AB₂(g) ↔ A(g) + 2B(g) Kc₁= 1/59
A(g) + 3B(g) ↔ AB₃(g) Kc₂= 478
-----------------------------------------
AB₂(g) + B(g) ↔ AB₃(g)
If we add reactions at equilibrium, the equilibrium constants Kc are mutiplied as follows:
Kc = Kc₁ x Kc₂ = 1/59 x 478 = 478/59 = 8.10
The value of the missing equilibrium constant is 8.10.
The value of the missing equilibrium constant is 8.10
Chemical Equations:Since
A(g) + 2B(g) ↔ AB₂(g) Kc = 59 ---- Eq. 1
A(g) + 3B(g) ↔ AB₃(g) Kc = 478 ----- Eq. 2
Now we have to rearrange the chemical equations in order to obtain:
AB₂(g) + B(g) ↔ AB₃(g) Kc = ?
Here AB₂(g) represents a reactant, so we have to applied the reverse reaction of Eq. 1, in this case Kc= 1/59. Since AB₃(g) is a product, we use the forward reaction of Eq.2, and the constant should be the same: Kc= 478.
The following is the sum of rearranged chemical equations, and the compounds in bold and italic should be canceled:
AB₂(g) ↔ A(g) + 2B(g) Kc₁= 1/59
A(g) + 3B(g) ↔ AB₃(g) Kc₂= 478
-----------------------------------------
AB₂(g) + B(g) ↔ AB₃(g)
In the case when we add reactions at equilibrium, the equilibrium constants Kc are multiplied as follows:
Kc = Kc₁ x Kc₂ = 1/59 x 478 = 478/59 = 8.10
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What is the total number of electrons that can occupy the p sublevel? (3 points)
Select one:
a. 2 electrons
b. 6 electrons
c. 8 electrons
d. 10 electrons
Answer:
The answer is 6 because the p sublevel holds 3 orbitals and since each orbital can hold 2 electrons, the answer is 3 * 2 = 6.
Answer:
6 electrons
Explanation:
Each principal energy level above the first contains one s orbital and three p orbitals. A set of three p orbitals, called the p sublevel, can hold a maximum of six electrons. So the answer is 6 electrons.
Calculate the value of ΔG∘rxnΔGrxn∘ for the following reaction at 296 K. Ka = 2.9 × 10–8 and assume Ka does not change significantly with temperature. $$HClO(aq)+H2O(l) HClO−(aq)+H3O+(aq)
Answer:
[tex]\Delta G_{rxn}=42.7\frac{kJ}{mol}[/tex]
Explanation:
In this case, for the dissociation of hypochlorous acid, we know that the acid dissociation constant (Ka) is 2.9x10⁻⁸, which is related with the Gibbs free energy as shown below:
[tex]\Delta G_{rxn}=-RTln(K)[/tex]
But in this case K is just Ka, therefore, at 296 K, it turns out:
[tex]\Delta G_{rxn}=-8.314\frac{J}{mol*K}*296K*ln(2.9x10^{-8})\\\\\Delta G_{rxn}=42.7\frac{kJ}{mol}[/tex]
Such result, means that the reaction is nonspontaneous at the given temperature, it means it is not favorable (not easily occurring).
Best regards.
For the following reaction at equilibrium, which gives a change that will shift the position of equilibrium to favor formation of more products? 2NOBr(g) 2NO(g) + Br 2(g), ΔHº rxn = 30 kJ/mol
Answer:
Based on the given reaction, it is evident that the reaction is endothermic as indicated by a positive sign of enthalpy of reaction. Thus, it can be stated that the favoring of the forward reaction will take place by upsurging the temperature of the reaction mixture.
Apart from this, based on Le Chatelier’s principle, any modification in the quantity of any species is performed at equilibrium and the reaction will move in such an orientation so that the effect of the change gets minimized. Therefore, a slight enhancement in the concentration of the reactant will accelerate the reaction in the forward direction and hence more formation of the product takes place.
When the owners of some wells in Pallerla started using high-powered motors to
draw water from the wells, the owners of other wells noticed that their wells were
drying up. Discuss the possible solution to the problem solutions to the problem
Answer:
The possible solution is to balance the rate of water removal from the well to the rate of natural recharge of the well from its underground aquifer.
Explanation:
A well is an excavation in the earth, made with the aim of extracting water from the aquifers. The water from a well can be drawn up by the means of a pump, containers, such as buckets, or by hand. Aquifers can also be recharged through a well.
Well draw down occurs when water from the well is drained faster than it is naturally recharged from the aquifer. This can be as a result of over pumping, extended drought, among other factors. The use of the high-powered motor in this case, for pumping, might be the possible cause of the well drying up. The situation might have resulted from the pump drawing out water from the well at a rate tat exceeds the rate at which it is recharged naturally, causing the well water to start drying up. There's also a possibility that the well is pumped indiscriminately, possibly leading to wastage of water.
The solution to this problem is to give the well a time duration for it to recharge itself. Then, the rate of recharges should be calculated and determined by an hydrologist. When all these is done, a pump with a motor power that does not exceed the calculated recharge rate should be used in place of the high-powered motor. Also, water usage should be brought to the minimum level to prevent unnecessary pumping due to excessive, wasteful use of water.
Question 5 options: The cell potential for an electrochemical cell with a Zn, Zn2 half-cell and an Al, Al3 half-cell is _____ V. Enter your answer to the hundredths place and do not leave out a leading zero, if it is needed.
Answer:
The voltage is [tex]E_{cell} = 0.944 \ V[/tex]
Explanation:
Generally the half reaction for Zn, Zn2 half-cell is mathematically represented as
[tex]Zn_{(s)}[/tex] ⇔ [tex]Zn^{2+}_{ (aq)} + 2e^-[/tex] (reference study academy)
and the electric potential for this is a constant value
[tex]E_{zn } = -0.7618 \ V[/tex]
Generally the half reaction for Al, Al3 half-cell is mathematically represented as
[tex]Al^{3+} _{(aq)} + 3e^-[/tex] ⇔ [tex]Al_{(s)}[/tex]
and the electric potential for this is constant value
[tex]E_{Al } = -1.662 \ V[/tex]
Therefore the cell potential for an electrochemical cell is mathematically represented as
[tex]E_{cell} = E_{zn } - E_{Al }[/tex]
substituting values
[tex]E_{cell} = -0.718 - (-1.662)[/tex]
[tex]E_{cell} = 0.944 \ V[/tex]
Which of these are elimination reactions? Check all that apply.
CH3OH + CH3COOH → CH3CO2CH3 + H20
C3H7OH → C3H6 + H20
H9C2Br + NaOH → C2H4 + NaBr + H20
Answer:
C3H7OH → C3H6 + H20
Explanation:
If we look at the reactant and the product we will realize that the reactant is an alcohol while the product is an alkene. The reaction involves acid catalysed elimination of water from an alcohol.
Water is a good leaving group, hence an important synthetic route to alkenes is the acid catalysed elimination of water from alcohols. Hence the conversion represented by C3H7OH → C3H6 + H20 is an elimination reaction in which water is the leaving group.
Answer:
B and C. Just finished my lesson on Edge.
Question 7 options: The cell potential of an electrochemical cell made of an Fe, Fe2 half-cell and a Pb, Pb2 half-cell is _____ V. Enter your answer to the hundredths place and do not leave off the leading zero, if needed.
Answer: Thus the cell potential of an electrochemical cell is +0.28 V
Explanation:
The calculation of cell potential is done by :
[tex]E^0=E^0_{cathode}- E^0_{anode}[/tex]
Where both [tex]E^0[/tex] are standard reduction potentials.
[tex]E^0_{[Fe^{2+}/Fe]}= -0.41V[/tex]
[tex]E^0_{[Pb^{2+}/Pb]}=-0.13V[/tex]
As Reduction takes place easily if the standard reduction potential is higher(positive) and oxidation takes place easily if the standard reduction potential is less(more negative). Thus iron acts as anode and lead acts as cathode.
[tex]E^0=E^0_{[Pb^{2+}/Pb]}- E^0_{[Fe^{2+}/Fe]}[/tex]
[tex]E^0=-0.13- (-0.41V)=0.28V[/tex]
Thus the cell potential of an electrochemical cell is +0.28 V
When alkanes react with chlorine in the presence of ultraviolet light, chlorine atoms substitute for one or more alkane hydrogen atoms. What is the number of different chloroalkane compounds that can be formed by the reaction of C2H6 with chlorine?
Answer:
6
Explanation:
Alkanes undergo substitution reaction so the number of replacement reaction hydrogen is 6
A major component of gasoline is octane, C8H18. When octane is burned in air, it chemically reacts with oxygen gas (O2) to produce carbon dioxide (CO2) and water (H2O) . What mass of carbon dioxide is produced by the reaction of 3.2g of oxygen gas? Round your answer to 2 significant digits.
Answer:
[tex]m_{CO_2}=2.8gCO_2[/tex]
Explanation:
Hello,
In this case, the combustion of octane is chemically expressed by:
[tex]C_8H_{18}+\frac{25}{2} O_2\rightarrow 8CO_2+9H_2O[/tex]
In such a way, due to the 25/2:8 molar ratio between oxygen and carbon dioxide, we can compute the yielded grams of carbon dioxide (molar mass 44 g/mol) as shown below:
[tex]m_{CO_2}=3.2gO_2*\frac{1molO_2}{32gO_2} *\frac{8molCO_2}{\frac{25}{2}molO_2 } *\frac{44gCO_2}{1molCO_2}\\ \\m_{CO_2}=2.8gCO_2[/tex]
Best regards.
What are representative elements"?
A. Elements in the short columns of the periodic table
B. Elements in the same row of the periodic table
C. Elements that share the same properties on the periodic table
D. Elements in the tall columns of the periodic table
The representative elements are the elements in the tall columns of the periodic table.
What are the representative elements?The representative elements that can also be referred to as the main group elements. They can be used to represent the chemistry of the group to which they belong.
Hence, the representative elements are the elements in the tall columns of the periodic table.
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After heating a sample of hydrated CuSO4, the mass of released H2O was found to be 2.0 g. How many moles of H2O were released if the molar mass of H2O is 18.016 g/mol
Answer:
0.1110 mol
Explanation:
Mass = 2g
Molar mass = 18.016 g/mol
moles = ?
These quantities are realted by the following equation;
Moles = Mass / Molar mass
Substituting the values of the quantities and solving for moles, we have;
Moles = 2 / 18.016 = 0.1110 mol
Write electron configurations for the following ion: Cd2 Cd2 . Express your answer in order of increasing orbital energy. For example, the electron configuration of LiLi would be entered in complete form as 1s^22s^1 or in condensed form as [He]2s^1.
Answer:
Cd2+ : 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10 or [Kr] 4d¹⁰
Explanation:
Before proceeding to write out the electron configuration of Cd2+, we have to obtain the electron configuration of Cadmium (Cd),
Cadmium has an atomic number of 48, this means that a neutral cadmium atom will have a total of 48 electrons surrounding its nucleus.
The electronic configuration of Cadmium is;
Cd: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10
The shorthand notation is given as;
Cd: [Kr] 4d¹⁰5s²
Cd2+ means that it has two less electrons, hence it's electron configuration is given as;
Cd2+ : 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10 or [Kr] 4d¹⁰
Calculate the heat absorbed by a sample of water that has a mass of 45.00 g when the temperature increases from 21.0oC to 38.5 oC. (s=4.184 J/g.o C)
Answer:
The heat absorbed by the sample of water is 3,294.9 J
Explanation:
Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.
The sensible heat of a body is the amount of heat received or transferred by a body when it undergoes a temperature variation (Δt) without there being a change of physical state (solid, liquid or gaseous). Its mathematical expression is:
Q = c * m * ΔT
Where Q is the heat exchanged by a body of mass m, made up of a specific heat substance c and where ΔT is the temperature variation.
In this case:
Q=?m= 45 gc= 4.184 [tex]\frac{J}{g*C}[/tex]ΔT= Tfinal - Tinitial= 38.5 C - 21 C= 17.5 CReplacing:
Q= 4.184 [tex]\frac{J}{g*C}[/tex] * 45 g* 17.5 C
Solving:
Q=3,294.9 J
The heat absorbed by the sample of water is 3,294.9 J
Write the equilibrium constant expression for the experiment you will be studying this week. 2. If the equilibrium values of Fe3+, SCN- and FeSCN2+ are 9.5 x 10-4 M, 3.6 x 10-4 M and 5.7 x 10-5 M respectively, what is the value of Kc? 3. Write the general form of the dilution equation. 4. A solution is prepared by adding 18 mL of 0.200 M Fe(NO3)3 and 2 mL of 0.0020 M KSCN. Calculate the initial concentrations of Fe3+ and SCNin the solution.
Answer:
Kc = 166.7
[Fe³⁺] = 0.18 M
[SCN⁻] = 2×10⁻⁴ M
Explanation:
In the reaction of Fe³⁺ and SCN⁻, it is formed a complex:
Fe³⁺ + SCN⁻ ⇄ FeSCN²⁺ Kc
Let's make the expression for Kc → [FeSCN²⁺] / [Fe³⁺] . [SCN⁻]
5.7×10⁻⁵ / 9.5×10⁻⁴. 3.6×10⁻⁴ = 166.7
We determine the mmoles, we add from each reactant:
18 ml . 0.2M = 3.6 mmoles of Fe³⁺
2 ml . 0.002M = 4×10⁻³ mmoles of SCN⁻
General form of the dilution equation is:
Concentrated [C] . Concentrated Volume = Diluted [C] . Diluted Volume
Total volume = 20mL
[Fe³⁺]: 3.6 mmoles /20mL = 0.18 M
[SCN⁻]: 4×10⁻³ mmoles /20mL = 2×10⁻⁴ M
The value should be 1.67 x 10^2
The initial concentration should be 0.18 M and 2.0 x 10^(-4) M
Calculation of the value and initial concentration:The value is
= 5.7 x 10^(-5)/(9.5 x 10^(-4) x 3.6 x 10^(-4))
= 167
= 1.67 x 10^2
we know that
Initial moles = volume x concentration
So,
= 18/1000 x 0.200
= 0.0036 mol
Now
Initial moles = volume x concentration
= 2/1000 x 0.0020
= 4.0 x 10^(-6) mol
So,
Total volume should be
= 18 + 2
= 20 mL
= 0.02 L
Now
Initial concentration
= moles /total volume
= 0.0036/0.02
= 0.18 M
Now
Initial concentration
= moles /total volume
= 4.0 x 10^(-6)/0.02
= 2.0 x 10^(-4) M
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After the reaction between sodium borohydride and the ketone is complete, the reaction mixture is treated with water and H2SO4 to produce the desired alcohol. Explain the reaction by clearly indicating the source of the hydrogen atom that ends up on the oxygen
Answer:
The hydrogen can be gotten from the added Acid or water during "workup".
Explanation:
Basically we can say that the reaction describe in this question is a Reduction reaction because of the chemical compound called sodium borohydride. In the reaction described above we can see that there is a Reduction of ketone to alcohol by the compound; sodium borohydride.
For the reduction Reaction to occur the C-O bond must break so as to enable the formation of O-H bond and C-H bond.
So, "the reaction mixture is treated with water and H2SO4 to produce the desired alcohol", thus, the oxygen will definitely pick up the hydrogen from H2SO4 or H2O.
For each of the following, classify the substance as a strong acid, strong base, weak acid, or weak base (or perhaps not acidic or basic). Then determine the pH of the solution and calculate the concentrations of all aqueous species present in the solution.a. 2.0 × 10 ^–2 M HBrb. 1.0 × 10^–4 M NaOHc. 0.0015 M Ba(OH)2 d. 0.25 M HCN e. 2.0 × 10 ^–10 M KOH f. 0.050 M NH3 g. 0.100 M NH4Cl h. 0.200 M CaF2 i. 0.0500 M Ba(NO3)2 j. 0.100 M Al(NO3)3
Answer:
a. Strong acid, pH = 1.69
b. Strong base, pH = 10
c. Strong base, pH = 11
d. Weak acid, pH = 4.90
e. Strong base, pH ≅ 7 (pH should be higher than 7, but the base is so diluted)
f. Weak base, pH = 10.96
g. Acidic salt, pH = 5.12
h. Basic salt, pH = 8.38
i. Neutral salt, pH = 7
j. Acidic salt, pH < 7
Explanation:
a. HBr → H⁺ + Br⁻
Hydrobromic acid is a strong acid.
pH = - log [H⁺]
- log 0.02 = 1.69
b. NaOH → Na⁺ + OH⁻
Sodium hydroxide is a strong base.
pH = 14 - pOH
pOH = - log [OH⁻]
pH = 14 - (-log 0.0001) = 10
c. Ba(OH)₂ → Ba²⁺ + 2OH⁻
Barium hydroxide is a strong base
[OH⁻] = 2 . 0.0015 = 0.003M
pH = 14 - (-log 0.003) = 11
d. HCN + H₂O ⇄ H₃O⁺ + CN⁻
This is a weak acid, it reacts in water to make an equilibrium between the given protons and cyanide anion.
To calculate the [H₃O⁺] we must apply, the Ka
Ka = [H₃O⁺] . [CN⁻] / [HCN]
6.2×10⁻¹⁰ = x² / 0.25-x
As Ka is really small, we can not consider the x in the divisor, so we avoid the quadratic formula.
[H₃O⁺] = √(6.2×10⁻¹⁰ . 0.25) = 1.24×10⁻⁵
-log 1.24×10⁻⁵ = 4.90 → pH
e. KOH → K⁺ + OH⁻
2×10⁻¹⁰ M → It is a very diluted concentration, so we must consider the OH⁻ which are given, by water.
In this case, we propose the mass and charges balances equations.
Analytic concentration of base = 2×10⁻¹⁰ M = K⁺
[OH⁻] = K⁺ + H⁺ → Charges balance
The solution's hydroxides are given by water and the strong base.
Remember that Kw = H⁺ . OH⁻, so H⁺ = Kw/OH⁻
[OH⁻] = K⁺ + Kw/OH⁻. Let's solve the quadratic equation.
[OH⁻] = 2×10⁻¹⁰ + 1×10⁻¹⁴ /OH⁻
OH⁻² = 2×10⁻¹⁰. OH⁻ + 1×10⁻¹⁴
2×10⁻¹⁰. OH⁻ + 1×10⁻¹⁴ - OH⁻²
We finally arrived at the answer [OH⁻] = 1.001ₓ10⁻⁷
pH = 14 - (- log1.001ₓ10⁻⁷) = 7
The strong base is soo diluted, that water makes the pH be a neutral value.
Be careful, if you determine the [OH⁻] as - log 2×10⁻¹⁰, because you will obtain as pOH 9.69, so the pH would be 4.31. It is not possible, KOH is a strong base and 4.30 is an acid pH.
f. Ammonia is a weak base.
NH₃ + H₂O ⇄ NH₄⁺ + OH⁻
Kb = OH⁻ . NH₄⁺ / NH₃
1.74×10⁻⁵ = x² / 0.05 - x
We can avoid the x from the divisor, so:
[OH⁻] = √(1.74×10⁻⁵ . 0.05) = 9.32×10⁻⁴
pH = 14 - (-log 9.32×10⁻⁴ ) = 10.96
g. NH₄Cl, an acid salt. We dissociate the compound:
NH₄Cl → NH₄⁺ + Cl⁻. We analyse the ions:
Cl⁻ does not make hydrolisis to water. In the opposide, the ammonium can react given OH⁻ to medium, that's why the salt is acid, and pH sould be lower than 7
NH₄⁺ + H₂O ⇄ NH₃ + H₃O⁺ Ka
Ka = NH₃ . H₃O⁺ / NH₄⁺
5.70×10⁻¹⁰ = x² / 0.1 -x
[H₃O⁺] = √ (5.70×10⁻¹⁰ . 0.1) = 7.55×10⁻⁶
pH = - log 7.55×10⁻⁶ = 5.12
As Ka is so small, we avoid the x from the divisor.
h. CaF₂ → Ca²⁺ + 2F⁻
This is a basic salt.
The Ca²⁺ does not react to water. F⁻ can make hydrolisis because, the anion is the strong conjugate base, of a weak acid.
F⁻ + H₂O ⇄ HF + OH⁻ Kb
Kb = x² / 2 . 0.2 - x
Remember that, in the original salt we have an stoichiometry of 1:2, so 1 mol of calcium flouride may have 2 moles of flourides.
As Kb is small, we avoid the x, so:
[OH⁻] = √(1.47×10⁻¹¹ . 2 . 0.2) = 2.42×10⁻⁵
14 - (-log 2.42×10⁻⁵) = pH → 8.38
i . Neutral salt
BaNO₃₂ → Ba²⁺ + 2NO₃⁻
Ba²⁺ comes from a strong base, so it is the conjugate weak acid and it does not react to water. The same situation to the nitrate anion. (The conjugate weak base, from a strong acid, HNO₃)
pH = 7
j. Al(NO₃)₃, this is an acid salt.
Al(NO₃)₃ → Al³⁺ + 3NO₃⁻
The nitrate anion is the conjugate weak base, from a strong acid, HNO₃ so it does not make hydrolisis. The Al³⁺ comes from the Al(OH)₃ which is an amphoterous compound (it can react as an acid or a base) but the cation has an acidic power.
Al·(H₂O)₆³⁺ + H₂O ⇄ Al·(H₂O)₅(OH)²⁺ + H₃O⁺