About what fraction of Earth’s surface is covered by water?
A:1/4
B:1/2
C:3/4
D:9/10

Answer:

the answer is B. the energy required to go from a solid to liquid

B. The latent heat of fusion is the energy required to go from a solid to a liquid. It is the amount of heat energy that must be added to a substance at its melting point to convert it from a solid to a liquid, without changing its temperature.

Latent heat is the amount of heat energy required to change the phase of a substance without changing its temperature.

Option A describes the energy required to break molecular bonds, which is called the bond dissociation energy.

Option C describes the energy required to go from a solid to a gas, which is called the latent heat of sublimation.

Option D describes the energy required to go from a liquid to a gas, which is called the latent heat of vaporization.

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The following substances does not exist in the indicated solid type : c.) SiO₂- molecular.

SiO2 is a covalent solid and the solid state of silicon dioxide (SiO2) is a covalent crystal with sharing of valence electrons between the silicon atom and oxygen atoms.

Silicon dioxide is a silicon oxide made of linear triatomic molecules in which silicon atom is covalently bonded to two oxygens. Silicon dioxide which is often called silica is the main compound found in sand.

Silicon dioxide is not soluble in water as the interaction between SiO2 and water molecules is not sufficient to overcome the strong and extensive covalent bonds in giant molecule.

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Explanation:

Causes of climate change are:

1.)Smoke from Vehicles and industrial activities

2.) Burning of polythenes.

3.) Because of green house effect

Effects are:

1.) Extinction of birds,plants and animals

2.) Melting of glaciers

3.) Rise in global temperature

Given :

Mass of gold ( Au ) is 212 gram.

To Find :

Atoms of gold present in 212 gram of gold.

Solution :

Molecular mass of gold is 197 gram.

So, number of moles of gold in 212 gram is :

[tex]n = \dfrac{212}{197} \ moles\\\\n = 1.076 \ moles[/tex]

Now, we know 1 mole of any element contains [tex]6.022 \times 10^{23}[/tex] atoms.

So, number of atoms present in 1.076 moles are :

[tex]N = 1.076 \times 6.022\times 10^{23}\\\\N = 6.48 \times 10^{23}[/tex]

Hence, this is the required solution.

Answer:

electron are on the outside of the nucleus and form rings

Explanation:

At a pressure of 12.4 atm and a temperature of 850 c, 8.2 liters of water can be created from 55 grams of oxygen gas and an excess of hydrogen.

first, we need the no.of moles of O2 = mass/molar mass of O2

                                                            = 55 g / 32 g/mol

                                                            = 1.72 mol

from the balanced equation of the reaction:

2H2 (g) + O2(g) → 2H2O(g)

we can see that the molar ratio between O2: H2O = 1: 2

So we can get the no.of moles of H2O = 2 * moles of O2

                                                                 = 2 * 1.72 mol

                                                                 = 3.44 mol

So by substitution by this value in the ideal gas formula:

PV = nRT

when P = 12.4 atm  & n H2O = 3.44 mol & R= 0.0821 & T = 85 + 273=358K

12.4 atm *V = 3.44 * 0.0821 * 358 = 8.15 L

∴ V ≈ 8.2 L

In the physical sciences, pressure is defined as the perpendicular force per unit area or stress at a point within a confined fluid. The pressure exerted on a floor by a 42-pound box with a bottom area of 84 square inches is equal to the force divided by the area over which it is exerted, or one-half pound per square inch.

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Taking into account the reaction stoichiometry, 40 grams of O₂ are needed to react with 0.50 moles of C₂H₂.

In first place, the balanced reaction is:

2 C₂H₂ + 5 O₂ → 4 CO₂ + 2 H₂O

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

The molar mass of the compounds is:

Then, by reaction stoichiometry, the following mass quantities of each compound participate in the reaction:

The following rule of three can be applied: if by stoichiometry of the reaction 2 moles of C₂H₂ react with 160 grams of O₂, 0.50 moles of C₂H₂ react with how much mass of O₂?

[tex]mass of O_{2} =\frac{0.50 moles of C_{2} H_{2}x160 grams of O_{2} }{2 moles of C_{2} H_{2}}[/tex]

mass of O₂= 40 grams

Finally, 40 grams of O₂ are needed to react with 0.50 moles of C₂H₂.

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Answer:

Question: What is heat?

Answer: Heat is a form of energy It can be transferred but not destroyed and is the energy that flows from a hotter object to a less hot to a cold one due to a temperature difference between the objects, meaning an object would continually be cold unless it acquires heat from a hot object or source through heat transfer mechanisms which can be conduction, convection, or radiation, and it is measured usually in calories or joules.

Question: In which direction does heat flow?

Answer: Heat practically flows from a hot object which has a higher temperature to a cold object which temperature is lower through conduction, convection, radiation.

Question: What does thermochemistry involve?

Answer: Thermochemistry is the study of heat as a form of energy making it possible to determine the relationship between heat and chemical reactions which is necessary to know if a reaction would take place or not.

Question: How do we measure heat?

Answer: it is measured usually in calories or joules using thermometers and pyrometers.

The equilibrium concentration of B is 0.325 mol/L.

The correct option is B.

The equilibrium concentration of B in the given reaction is calculated below as follows:

The concentration of A at equilibrium, [A]  = 0.246 mol/L

Constructing an ICE table

          A(g)     +      2B (g)   →      C(g)

I         2 mole         3 moles           -

C      0.524            1.048            0.524

E        0.246         (3 - 1.048) / 6

From the equation of the reaction:

(2 - x) / 6L  =  0.246 mol/L

2 - x = 0.246 * 6

2 - x = 1.476

x = 2 - 1.476

x = 0.524 moles

[B] = (3 - 1.048) / 6

[B] = 0.325 mol/L

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Complete question:

For the reaction given below, 2.00 moles of A and 3.00 moles of B are placed in a 6.00-L container.

A(g) + 2B(g) C(g)

At equilibrium, the concentration of A is 0.246 mol/L. What is the concentration of B at equilibrium? A) 0.246 mol/L B) 0.325 mol/L C) 0.500 mol/L D) 0.492 mol/L E) none of these

Answer:

1. Hydrogen ions; acidic

2. Alkali; hydroxide ions; alkaline

3a. Sulfuric acid --> 2 Hydrogen ions + sulfate ion

H₂SO₄ --> 2H+ + SO₄²-

3b. Sodium hydroxide --> Sodium ion + Hydroxide ion

NaOH --> Na+ + OH-

Explanation:

1. Sulfuric acid releases hydrogen ions in solution. This makes the solution acidic.

Acids produce hydrogen ions when dissolved in aqueous solutions.

2. Sodium hydroxide is an alkali. It releases hydroxide ions in solution. This makes the solution alkaline.

Alkalis are soluble bases that produce hydroxide ions in solution.

3a. Sulfuric acid --> 2 Hydrogen ions + sulfate ions

H₂SO₄ --> 2H+ + SO₄²-

The equation above is for the ionization of sulfuric acid

b. Sodium hydroxide --> Sodium ion + Hydroxide ion

NaOH --> Na+ + OH-

The equation above is for the ionization of sodium hydroxide

The conservation of natural resources be most effective in reducing carbon dioxide in the atmosphere,  is the planting more trees.

The planting the more new tress is the one of the most effective ways to reduce the atmospheric carbon dioxide. this will also limits the global warming. the plants remove the carbon dioxide from the atmosphere through the photosynthesis. plants helps to stop the climate change as they will remove the carbon dioxide from the atmosphere. and  store the carbon in tress and the soil.

Thus , the way to reduce the carbon dioxide from the atmosphere is the planting more and more trees.

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AThe half-life of an isotope is the amount of time it takes for half of the atoms in a sample to decay. If the half-life of a sample of uranium-234 is 2.5 * 10^5 years, it means that after 2.5 * 10^5 years, half of the atoms in the sample will have decayed.

If you want to know how long it will take for only one sixth of the original mass to be left, you can use the following formula:

t = (half-life) * log(2) / log(1/6)

Plugging in the values, we get:

t = (2.5 * 10^5 years) * log(2) / log(1/6)

This simplifies to:

t = 3.7 * 10^5 years

So it will take approximately 3.7 * 10^5 years for only one sixth of the original mass to be left.nswer:

Answer:

the red one

Explanation:

you can see in the picture

To determine the pressure of a gas, we need to use the ideal gas law, which states that PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin.

We can re-arrange the ideal gas law to solve for pressure:

P = (nRT) / V

We are given that the density of the gas is 3.10 g/L, which we can use to calculate the volume of the gas. Density is defined as mass/volume, so we can rearrange the equation to find volume:

V = mass/density

We know the density is 3.10 g/L, and the mass is n * molar mass of N2O.

Molar mass of N2O = (14.01 + 2 * 16.00) g/mol = 44.01 g/mol

The volume of the gas is:

V = mass / density = n * molar mass of N2O / 3.10 g/L

Now we have all the information needed to use the ideal gas law to determine the pressure of the gas.

We are given that the temperature of the gas is 298K.

We can use the ideal gas constant R = 0.0821 Latm/molK

Plugging in the known values:

P = (nRT) / V = (n * 0.0821 Latm/molK * 298K) / (n * molar mass of N2O / 3.10 g/L)

P = (0.0821 * 298) / (44.01 / 3.10) atm

To convert the pressure in atm to mmHg, we need to multiply the pressure by 760 (1 atm = 760 mmHg)

P = (0.0821 * 298) / (44.01 / 3.10) * 760 mmHg

The pressure of the N2O gas is approximately 739.07 mmHg at 298K and density of 3.10 g/L.

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The following geometry for the complex ion [Fe(en)Cl4] is : octahedral.

The arrangement of atoms in a molecule in three dimensions is known as molecular geometry, commonly referred to as the molecular structure. A compound's polarity, reactivity, phase of matter, color, magnetism, and biological activity can be determined by knowing its molecular structure.

Tetrahedral molecular geometry is present here (e.g. CH4). Trigonal pyramidal molecular geometry results from having three bond pairs and one lone pair of electrons (e.g. NH3). The geometry of the molecule is angular or curved if there are two bond pairs and two lone pairs of electrons (e.g. H2O).

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Answer:

1. Vinegar.

2. a solution is a special type of homogeneous mixture composed of two or more substances.

* Hypertonic

* isotonic

* hypotonic

Answer:

"457.2 mm.Hg" is the right solution.

Explanation:

Given:

Pressure,

[tex]P_1=600 \ mm.Hg[/tex]

[tex]P_2 = ?\\[/tex]

Volume,

[tex]V_1=70.0 \ L[/tex]

[tex]V_2=90.0 \ L[/tex]

Temperature,

[tex]T_1=20^{\circ}[/tex]

or,

   [tex]=293 \ K[/tex]

[tex]T_2=15.0^{\circ}[/tex]

or,

    [tex]=288 \ K[/tex]

As we know,

⇒  [tex]\frac{P_1V_1}{T_1} =\frac{P_2V_2}{T_2}[/tex]

By putting all the given values in the above expression, we get

⇒  [tex]\frac{0.789\times 70}{293} =\frac{P_2\times 90}{288}[/tex]

⇒  [tex]0.188=\frac{P_2\times 90}{288}[/tex]

By applying cross-multiplication, we get

⇒  [tex]P_2=\frac{0.188\times 288}{90}[/tex]

⇒       [tex]=\frac{54.144}{90}[/tex]

⇒       [tex]=0.6016 \ atm[/tex]

or,

⇒       [tex]=457.2 \ mm.Hg[/tex]

There would be 13.9 moles of the water.

We know that we could be able to use the Avogadro's number so as to determine the number of the molecules. this would stem from the postulation that one  mole of the substances would in it about 6.02 * 10^23 molecules of the water.

We would now be able to say based on the information that have been passed above in the question;

1 mole of water would contain 6.02 * 10^23 molecules of the water

x moles of water would contain 8.37 x 10^24 molecules

x = 8.37 x 10^24 molecules * 1/6.02 * 10^23

x = 13.9 moles

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The energy that is released for the breaking of bonds is 229 kJ/mol.

We should be able to recall that the enthalpy of the reaction taken to be the energy that is evolved or absorbed in the reaction that is ongoing. We have to note that in the course of the reaction there would be the breaking and the making of bonds.

Now we know that;

The bond energy can be given as;

Sum energy of the broken bonds of reactants  - Sum of the energy of the formed bonds

Hence;

(945 + 498) - 2(607)

1443 - 1214

= 229 kJ/mol

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Remove dry chemicals.Remove contaminated clothing or jewelry. Bandage the burn. Rinse again if needed.

the amount of harm to the skin relies upon on how strong the chemical was, how lots of it become at the skin, and how long it become there. Chemical burns, even minor ones, can be very painful. A minor burn may heal inside a few days. however a extra extreme burn might also take weeks or maybe months to heal completely.you need to now not use ice, or even ice-bloodless water, on a burn. extreme cold carried out to a burn can further damage the tissue. to properly cool and clean a burn, remove any apparel that covers it.

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The average molecular velocity of the molecules will decrease as the reaction goes to completion at a constant temperature.

What is Molecular velocity?

Molecular velocity is the average speed of molecules in a sample of matter. It is determined by the temperature of the sample, with higher temperatures resulting in higher molecular velocities.

This is because the reaction produces a single product, meaning that the number of molecules in the reaction vessel is decreasing as the reaction goes to completion. As the number of molecules decreases, the average molecular velocity of the molecules decreases as well.

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Answer:

not balanced, oxygen, not equal

Explanation:

Alright, so let's go ahead and balance this equation!

The easiest way to do this is to take out a piece of paper and write down your elements on each side. Let's do it together:

--------------------------------------------------------------------------------------------------------------

[tex]2NaOH + H_{2} SO_{4}[/tex]  →  [tex]Na_{2}SO_{4} + H_{2}O[/tex]

Let's count the number of molecules for each element on both sides. Starting with the left side:

↓

[tex]2(NaOH) + H_{2} SO_{4}[/tex]

The coefficient of 2 in front of NaOH will be distributed to Na, O, and H. The subscripts for H and O only apply to themselves, so S will have only one molecule. Then our molecule counts for the reactant side (the left side) will be:

↓

Na:  2

 O:  2+4 = 6

 H:  2+2 = 4

 S:   1

↓

Now, let's move on to the right side:

[tex]Na_{2}SO_{4} + H_{2}O[/tex]

This side only has subscripts, no coefficients, so that means that any elements that don't have subscripts (S and the second O ) will have a count of one. Knowing this, our molecule count for the product side (right side) is:

↓

Na:  2

 O:  4+1 = 5

 H:  2

 S:   1

↓

Let's compare our counts now:

Left side:        Right side:

Na:  2             Na:  2

 O:  6               O:  5

 H:  4               H:  2

 S:   1                S:  1

We can see that our O and H molecule counts are different. So that means it's an unbalanced equation.

--------------------------------------------------------------------------------------------------------------

Therefore, your answer will be:

The equation is not balanced because the number of hydrogen atoms and oxygen atoms is not equal in the reactants and in the products.

The quantity of energy required to convert 0.562 kg ice at -20.0°C to steam at 250°C is equal to 1885.4 KJ.

The specific heat capacity can be described as the amount of energy needed to raise the temperature in one unit of material by one-degree celsius.

The addition or emission of heat from the system will the temperature of the substance will be changed:

Q = mCΔT

Given, the amount of ice, m = 0.562 Kg = 562 g

The change in the temperature = 100 -20 = 80°C

The specific heat capacity of the water, C = 4.18J/g°C

The specific heat capacity of the ice, C = 2.03 J/g°C

The phase transition from ice to steam:

H₁ = 562 × 2.03 × (0-(-20))

H₁ = 22,817 J = 22.8 KJ

The enthalpy of the fusion will be absorbed:

H₂ =  n × H(fus)

The number of moles of water = 562/18 = 31.22 mol

H₂ = 31.22 × 6.02 kJ/mol

H₂ = 187.95 KJ

Phase transition from water at 0°C to water at 100°C:

H₃ = 562 × 4.18 × 100

H₃ = 234 KJ

The phase transition from water at 100°C to steam at 100°C:

H₄ = n × H(vap)

H₄ = 31.22 × 40.7 kJ/mol

H₄  = 1270.65 KJ

The heat to make steam at a temperature of 250°C:

H₅ = m × S×ΔT

H₅ = 562 × 2.02 ×150 = 170 KJ

The total energy needed to convert  0.562 kg ice at -20.0°C to steam at 250.0°C:

H = H₁ + H₂+ H₃+ H₄ +H₅

H = 1885.4 KJ

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A solute is a species that dissolves within a liquid solvent to form a solution—a single, uniform mixture. The total volume of the solution can be expressed in liters.

The total amount of solute contained within can be expressed as a number of moles. The solute concentration in molarity is calculated by combining these two values. The molarity is expressed in "mol/L" according to the required calculation, though it is frequently written in "M" units.

The amount of a substance in a certain volume of solution is known as its molarity (M). Molarity is the ratio of a solute's moles to liters of solution. The molar concentration of a solution is another name for molarity.

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Answer:

D

Explanation:

1 mole of N2 reacts with 3 moles of H2

28 g of N2 reacts with 6g of H2

x will react with 5.8g of H2

x= (28*5.8)/6

= 27.0g

Both tests, one using heated copper sulfate pentahydrate with iron filings and sulfur, and the other using copper sulfate pentahydrate, produced gas production and color changes.

Iron sulfide, which is black in color, is created when iron (gray) and sulfur (yellow) mix chemically.

Fe(s) + S(s) -> FeS(s)

The water molecules in the crystal of copper sulfate-pentahydrate (blue) evaporate when heated, transforming it into anhydrous copper sulfate, which is white in color.

CuSO4.5H2O -> CuSO4 + 5H2O

As a result, both reactions have changed in color and chemical organization. It is considered a chemical change to heat crystals of hydrated copper sulphate. An aqueous solution of copper sulphate loses copper ions to iron. It is an isolated displacement reaction between two metals. In the activity series, iron comes after copper.

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Answer: Both resulted in color change, One involved chemical change while the other involved physical change.

Explanation:

B and E on edge.

Answer: distance to epicenter: 7600 km, s-wave travel time: 20 minutes