Practice Exercises - Gases and the Gas Laws - REVIEW OF MAJOR TOPICS - SAT Subject Test Chemistry

SAT Subject Test Chemistry




Practice Exercises

1. The most abundant element in Earth”s crust is

(A) sodium

(B) oxygen

(C) silicon

(D) aluminum

2. A compound that can be decomposed to produce oxygen gas in the lab is

(A) MnO2

(B) NaOH

(C) CO2

(D) KClO3

3. In the usual laboratory preparation equation for the reaction in question 2, what is the coefficient of O2?

(A) 1

(B) 2

(C) 3

(D) 4

4. In the graphic representation of the energy contents of the reactants and the resulting products in an exothermic reaction, the energy content would be

(A) higher for the reactants

(B) higher for the products

(C) the same for both

(D) impossible to determine

5. The process of separating components of a mixture by making use of the difference in their boiling points is called

(A) destructive distillation

(B) displacement

(C) fractional distillation

(D) filtration

6. When oxygen combines with an element to form a compound, the resulting compound is called

(A) a salt

(B) an oxide

(C) oxidation

(D) an oxalate

7. According to the activity chart of metals, which metal would react most vigorously in a dilute acid solution?

(A) zinc

(B) iron

(C) aluminum

(D) magnesium

8. Graham”s Law refers to

(A) boiling points of gases

(B) gaseous diffusion

(C) gas compression problems

(D) volume changes of gases when the temperature changes

9. When 200 milliliters of a gas at constant pressure is heated, its volume

(A) increases

(B) decreases

(C) remains unchanged

10. When 200 milliliters of a gas at constant pressure is heated from 0°C to 100°C, the volume must be multiplied by

(A) 0/100

(B) 100/0

(C) 273/373

(D) 373/273

11. If you wish to find the corrected volume of a gas that was at 20°C and 1 atmosphere pressure and conditions were changed to 0°C and 0.92 atmosphere pressure, by what fractions would you multiply the original volume?





12. When the level of mercury inside a gas tube is higher than the level in the reservoir, you find the correct pressure inside the tube by taking the outside pressure reading and ? the difference in the height of mercury.

(A) subtracting

(B) adding

(C) dividing by 13.6

(D) doing both (c) and (a)

13. If water is the liquid in question 12 instead of mercury, you can change the height difference to an equivalent mercury expression by

(A) dividing by 13.6

(B) multiplying by 13.6

(C) adding 13.6

(D) subtracting 13.6

14. Standard conditions are

(A) 0°C and 14.7 mm

(B) 273 K and 760 mm Hg

(C) 273°C and 760 mm Hg

(D) 4°C and 7.6 mm Hg

15. When a gas is collected over water, the pressure is corrected by

(A) adding the vapor pressure of water

(B) multiplying by the vapor pressure of water

(C) subtracting the vapor pressure of water at that temperature

(D) subtracting the temperature of the water from the vapor pressure.

16. At 5.00 atmospheres pressure and 70°C how many moles are present in 1.50 liters of O2 gas?

(A) 0.036

(B) 0.266

(C) 0.536

(D) 0.103

Directions: Every set of the given lettered choices below refers to the numbered questions immediately below it. For each numbered item, choose the one lettered choice that fits it best. Every choice in a set may be used once, more than once, or not at all.

Questions 17–20 refer to the following graphs:

17. Which is a graphic depiction of Boyle”s Law?

18. Which is a graphic depiction of Charles”s Law?

19. Which is a graphic depiction of the relationship of the pressure of a given volume of gas with the absolute temperature?

20. Which graph shows the distribution of molecules with respect to their kinetic energy at different temperatures?

Answers and Explanations

1. (B) Oxygen is the most abundant element in Earth”s crust, with 21% of its composition.

2. (D) KClO3 can be decomposed with heat to form KCl and O2.

3. (C) The equation is 2KClO3(s) → 2KCl(s) + 3O2(g)

4. (A) Since energy is given off in an exothermic reaction, the heat content of the reactants would be higher than the products.

5. (C) Fractional distillation can separate liquids of different boiling points.

6. (B) Oxygen compounds formed in combination reactions are called oxides.

7. (D) Magnesium, which is the most active of the given metals, will react to release hydrogen.

8. (B) Graham”s Law refers to gaseous diffusion or effusion.

9. (A) When confined gases at a constant pressure are heated, they expand.

10. (D) The temperature must be changed to absolute temperature by adding 273 to the Celsius readings.

11. (C) Since the temperature is decreasing, the volume must decrease with the temperature fraction, and, because the pressure is decreasing, the volume must increase. The correct answer does this.

12. (A) The level is higher because the pressure inside the tube is less than outside. You must subtract the height inside the tube from the outside pressure.

13. (A) If water is the liquid, you must divide by 13.6 to change the height to the equivalent height of mercury.

14. (B) The only correct indication of standard conditions is (B). It is usually stated as 273 K and 760 mm Hg. (Note: “mm” and “torr” are interchangeable.)

15. (C) Because the vapor pressure of water is a part of the pressure reading, it must be subtracted to get the atmospheric pressure.

16. (B) Using the general gas law, PV = nRT, convert 70°C to K by adding 273 = 343 K. Solving for n, you get

17. (C) Boyle”s Law is an inverse relationship. As the pressure increases, the volume decreases, as shown by the graph.

18. (A) Charles”s Law is a direct relationship. As the temperature increases, the volume increases.

19. (A) The relationship of pressure to absolute temperature while the volume is held constant is a direct one. As the temperature on a given volume increases, the pressure will increase.

20. (D) The graphs in (D) show the distributions of the kinetic energy of molecules at two different temperatures.