Question 1

Why does a hot air balloon rise when the air in the balloon is heated?

Accepted Answer

The hot air balloon rises because the gas inside it expands when heated, reducing its density compared to the cooler air outside. This decrease in density causes the balloon to become buoyant and rise.

Question 2

Which would always lead to an increase in the average kinetic energy of a gas?

Accepted Answer

The average kinetic energy of a gas is directly proportional to its temperature. Increasing the temperature of the gas (option D) will always lead to an increase in the average kinetic energy of the gas molecules, according to the kinetic theory of gases. Options A, B, and C involve changes in pressure, volume, or the number of molecules, which do not directly affect the average kinetic energy of the gas molecules unless these changes result in a temperature change.

Question 3

Which isn't a basic assumption of the kinetic theory?

Accepted Answer

All the options (A, B, C, D) are indeed basic assumptions of the kinetic theory of gases, which describes how gas particles move and interact.

Question 4

Which isn't one of the postulates of the kinetic molecular theory?

Accepted Answer

The kinetic molecular theory does not state that all particles have the same speed at a constant temperature; instead, it suggests that particles have a range of speeds, described by the Maxwell-Boltzmann distribution.

Question 5

Which isn't a postulate of the kinetic molecular theory?

Accepted Answer

The mass of a molecule is not considered negligibly small in the kinetic molecular theory. Instead, the theory assumes that the volume of a molecule is negligibly small compared to the container's volume, and it does not make any assumptions regarding the mass being negligible.

Question 6

If the average speed of O₂ molecules at STP is 4.3 x 10² meters per second, what is the average speed of H₂ molecules at the same temperature and pressure?

Accepted Answer

The average speed of gas molecules is inversely proportional to the square root of their molar mass. Since H2 is much lighter than O2, its molecules move faster. The molar mass of O2 is 32 g/mol and H2 is 2 g/mol. The speed ratio is sqrt(32/2) = 4, so the speed of H2 is 4 times that of O2, which is 4.3 x 10^2 m/s x 4 = 1.7 x 10^3 m/s.

Question 7

The root-mean-square speed of CH₄ molecules at 25°C is about 0.56 km/s. What is the root-mean-square speed of a H₂ molecule at 25°C?

Accepted Answer

The root-mean-square speed is inversely proportional to the square root of the molar mass. Since H2 is much lighter than CH4, its speed is higher. Calculating using the formula, the speed of H2 is approximately 1.6 km/s.

Question 8

Assume that a container is filled with a mixture of SO₃ and Ne. The molecular weight of SO₃ is 80 g/mol and the atomic weight of Ne is 20 g/mol. The average velocity of an SO₃ molecule is:

Accepted Answer

The average velocity of a gas molecule is inversely proportional to the square root of its molar mass. Since SO3 has four times the molar mass of Ne, its average velocity is half that of Ne.

Question 9

Which of the following gases would diffuse fastest at room temperature?

Accepted Answer

Ammonia (NH3) has the lowest molar mass among the given gases, which means it will diffuse faster according to Graham's law of effusion.

Question 10

Nitrogen and oxygen are allowed to effuse through a porous barrier at 295 K. If nitrogen effuses at a rate of 0.0355 moles per minute, what is the rate of effusion of oxygen?

Accepted Answer

The answer of Nitrogen and oxygen are allowed to effuse...

Question 11

²³⁵U (234.040947 amu) and ²³⁸U (235.043925 amu) are separated on the basis of the relative rates of diffusion of ²³⁵UF₆ and ²³⁸UF₆. Calculate the relative rates of diffusion of these two compounds.

Accepted Answer

The answer of ²³⁵U (234.040947 amu) and ²³⁸U (235.043925 amu)...

Question 12

The ideal gas equation predicts that a plot of the pressure times the volume of a gas versus the pressure of this gas should be a horizontal straight line at a fixed temperature. When these quantities are graphed for CO₂, however, we find that PV dips far below the theoretical straight line at first. This can be explained as follows.

Accepted Answer

The force of attraction between CO₂ molecules causes them to be closer together than predicted by the ideal gas law, resulting in a lower PV value.

Question 13

Calculate the volume of hydrogen bromide that can be prepared by reacting 10.0 grams of phosphorus tribromide with excess water at 21°C and 753 mmHg. PBr₃(l) + 3 H₂O(l) $\rightarrow$ 3 HBr(g) + H₃PO₃(aq)

Accepted Answer

The answer of Calculate the volume of hydrogen bromide that...

Question 14

Calculate the volume of oxygen at 0°C and 1 atm pressure that can be produced by decomposing 100 mL of hydrogen peroxide if this solution is 27.6% H₂O₂ by weight and the density is 1.09 g/cm³. 2 H₂O₂(l) $\rightarrow$ 2 H₂O(l) + O₂(g)

Accepted Answer

The answer of Calculate the volume of oxygen at 0°C...

Question 15

2.11 moles of C₃H₈ are allowed to burn in the presence of excess O₂ to form CO₂ and H₂O. C₃H₈(g) + 5 O₂(g) $\rightarrow$ 3 CO₂(g) + 4 H₂O(g) The carbon dioxide is isolated from all other gases and stored in a 1.25 L container at 0.00°C. What is the pressure in this container if the gas obeys the ideal gas equation?

Accepted Answer

The ideal gas equation is PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature. We can rearrange this equation to solve for P: P = nRT/V.We are given that n = 2.11 moles, V = 1.25 L, R = 0.0821 L*atm/(mol*K), and T = 0.00°C = 273.15 K. Plugging these values into the equation, we get:P = (2.11 moles * 0.0821 L*atm/(mol*K) * 273.15 K) / 1.25 L = 113 atmTherefore, the pressure in the container is 113 atm.

Question 16

What is the empirical formula of the only product of the following reaction __ N₂O₃(g) + __ O₃(g) $\rightarrow$ If 3.00 L of N₂O₃ react completely with 1.00 L of O₃ to give 6.00 L of the product, all gases measured at STP?

Accepted Answer

The reaction shows that 3 volumes of N2O3 react with 1 volume of O3 to produce 6 volumes of the product. This indicates that the product has a 1:1 ratio of nitrogen to oxygen atoms, which corresponds to NO2.

Question 17

Two identical flasks are at the same temperature. One is filled with 2 grams of hydrogen, the other with 28 grams of nitrogen gas. Which property would be significantly different for the two samples?

Accepted Answer

Density would be significantly different because the mass of nitrogen gas is much greater than that of hydrogen gas for the same volume, assuming both gases behave ideally and are at the same temperature and pressure.

Question 18

Cyclopropane, a gas containing only carbon and hydrogen, is an anesthetic. If 0.450 L of cyclopropane at 120°C and 0.720 atm reacts with excess O₂ to give 1.35 L of CO₂(g) and 1.35 L of H₂O(g) at the same temperature and pressure, what is the percent by weight of carbon in cyclopropane?

Accepted Answer

The balanced reaction is C3H6 + 4.5O2 → 3CO2 + 3H2O. From the volumes, 1 mole of C3H6 produces 3 moles of CO2, indicating 3 carbon atoms per molecule. The molar mass of C3H6 is 42 g/mol (3*12 for C + 6*1 for H), and the mass of carbon is 36 g (3*12). The percent by weight of carbon is (36/42)*100% = 85.7%.

Question 19

A metal reacts with acid to form hydrogen gas as shown by the following equation. M(s) + 2 H⁺(aq) $\rightarrow$ M²⁺(aq) + H₂(g) What is the atomic weight of this metal if 3.49 grams of the metal generates enough hydrogen collected over water to fill a bottle with a volume of 2.20 L at 25.0°C and 1.00 atmosphere pressure under conditions where the vapor pressure of the solution is 23.8 torr?

Accepted Answer

Using the ideal gas law and correcting for vapor pressure, the moles of hydrogen gas can be calculated. Then, using stoichiometry, the moles of metal can be determined. Dividing the mass of the metal by the moles gives the atomic weight, which is approximately 40.0 g/mol.

Quiz 6: Gases

Why does a hot air balloon rise when the air in the balloon is heated?

Which would always lead to an increase in the average kinetic energy of a gas?

Which isn't a basic assumption of the kinetic theory?

Which isn't one of the postulates of the kinetic molecular theory?

Which isn't a postulate of the kinetic molecular theory?

If the average speed of O₂ molecules at STP is 4.3 x 10² meters per second, what is the average speed of H₂ molecules at the same temperature and pressure?

The root-mean-square speed of CH₄ molecules at 25°C is about 0.56 km/s. What is the root-mean-square speed of a H₂ molecule at 25°C?

Assume that a container is filled with a mixture of SO₃ and Ne. The molecular weight of SO₃ is 80 g/mol and the atomic weight of Ne is 20 g/mol. The average velocity of an SO₃ molecule is:

Which of the following gases would diffuse fastest at room temperature?

Nitrogen and oxygen are allowed to effuse through a porous barrier at 295 K. If nitrogen effuses at a rate of 0.0355 moles per minute, what is the rate of effusion of oxygen?

²³⁵U (234.040947 amu) and ²³⁸U (235.043925 amu) are separated on the basis of the relative rates of diffusion of ²³⁵UF₆ and ²³⁸UF₆. Calculate the relative rates of diffusion of these two compounds.

Calculate the volume of hydrogen bromide that can be prepared by reacting 10.0 grams of phosphorus tribromide with excess water at 21°C and 753 mmHg. PBr₃(l) + 3 H₂O(l) $\rightarrow$ 3 HBr(g) + H₃PO₃(aq)

Calculate the volume of oxygen at 0°C and 1 atm pressure that can be produced by decomposing 100 mL of hydrogen peroxide if this solution is 27.6% H₂O₂ by weight and the density is 1.09 g/cm³. 2 H₂O₂(l) $\rightarrow$ 2 H₂O(l) + O₂(g)

What is the empirical formula of the only product of the following reaction N₂O₃(g) + O₃(g) $\rightarrow$ If 3.00 L of N₂O₃ react completely with 1.00 L of O₃ to give 6.00 L of the product, all gases measured at STP?

Two identical flasks are at the same temperature. One is filled with 2 grams of hydrogen, the other with 28 grams of nitrogen gas. Which property would be significantly different for the two samples?

Cyclopropane, a gas containing only carbon and hydrogen, is an anesthetic. If 0.450 L of cyclopropane at 120°C and 0.720 atm reacts with excess O₂ to give 1.35 L of CO₂(g) and 1.35 L of H₂O(g) at the same temperature and pressure, what is the percent by weight of carbon in cyclopropane?

Quiz 6: Gases

Why does a hot air balloon rise when the air in the balloon is heated?

Which would always lead to an increase in the average kinetic energy of a gas?

Which isn't a basic assumption of the kinetic theory?

Which isn't one of the postulates of the kinetic molecular theory?

Which isn't a postulate of the kinetic molecular theory?

If the average speed of O2 molecules at STP is 4.3 x 102 meters per second, what is the average speed of H2 molecules at the same temperature and pressure?

The root-mean-square speed of CH4 molecules at 25°C is about 0.56 km/s. What is the root-mean-square speed of a H2 molecule at 25°C?

Assume that a container is filled with a mixture of SO3 and Ne. The molecular weight of SO3 is 80 g/mol and the atomic weight of Ne is 20 g/mol. The average velocity of an SO3 molecule is:

Which of the following gases would diffuse fastest at room temperature?

Nitrogen and oxygen are allowed to effuse through a porous barrier at 295 K. If nitrogen effuses at a rate of 0.0355 moles per minute, what is the rate of effusion of oxygen?

235U (234.040947 amu) and 238U (235.043925 amu) are separated on the basis of the relative rates of diffusion of 235UF6 and 238UF6. Calculate the relative rates of diffusion of these two compounds.

Calculate the volume of hydrogen bromide that can be prepared by reacting 10.0 grams of phosphorus tribromide with excess water at 21°C and 753 mmHg. PBr3(l) + 3 H2O(l) →\rightarrow→ 3 HBr(g) + H3PO3(aq)

Calculate the volume of oxygen at 0°C and 1 atm pressure that can be produced by decomposing 100 mL of hydrogen peroxide if this solution is 27.6% H2O2 by weight and the density is 1.09 g/cm3. 2 H2O2(l) →\rightarrow→ 2 H2O(l) + O2(g)

What is the empirical formula of the only product of the following reaction __ N2O3(g) + __ O3(g) →\rightarrow→ If 3.00 L of N2O3 react completely with 1.00 L of O3 to give 6.00 L of the product, all gases measured at STP?

Two identical flasks are at the same temperature. One is filled with 2 grams of hydrogen, the other with 28 grams of nitrogen gas. Which property would be significantly different for the two samples?

Cyclopropane, a gas containing only carbon and hydrogen, is an anesthetic. If 0.450 L of cyclopropane at 120°C and 0.720 atm reacts with excess O2 to give 1.35 L of CO2(g) and 1.35 L of H2O(g) at the same temperature and pressure, what is the percent by weight of carbon in cyclopropane?

If the average speed of O₂ molecules at STP is 4.3 x 10² meters per second, what is the average speed of H₂ molecules at the same temperature and pressure?

The root-mean-square speed of CH₄ molecules at 25°C is about 0.56 km/s. What is the root-mean-square speed of a H₂ molecule at 25°C?

Assume that a container is filled with a mixture of SO₃ and Ne. The molecular weight of SO₃ is 80 g/mol and the atomic weight of Ne is 20 g/mol. The average velocity of an SO₃ molecule is:

²³⁵U (234.040947 amu) and ²³⁸U (235.043925 amu) are separated on the basis of the relative rates of diffusion of ²³⁵UF₆ and ²³⁸UF₆. Calculate the relative rates of diffusion of these two compounds.

Calculate the volume of hydrogen bromide that can be prepared by reacting 10.0 grams of phosphorus tribromide with excess water at 21°C and 753 mmHg. PBr₃(l) + 3 H₂O(l) $\rightarrow$ 3 HBr(g) + H₃PO₃(aq)

Calculate the volume of oxygen at 0°C and 1 atm pressure that can be produced by decomposing 100 mL of hydrogen peroxide if this solution is 27.6% H₂O₂ by weight and the density is 1.09 g/cm³. 2 H₂O₂(l) $\rightarrow$ 2 H₂O(l) + O₂(g)

What is the empirical formula of the only product of the following reaction N₂O₃(g) + O₃(g) $\rightarrow$ If 3.00 L of N₂O₃ react completely with 1.00 L of O₃ to give 6.00 L of the product, all gases measured at STP?

Cyclopropane, a gas containing only carbon and hydrogen, is an anesthetic. If 0.450 L of cyclopropane at 120°C and 0.720 atm reacts with excess O₂ to give 1.35 L of CO₂(g) and 1.35 L of H₂O(g) at the same temperature and pressure, what is the percent by weight of carbon in cyclopropane?