Unit 7& 8

Specific heat capacity is the quantity of heat required to raise the temperature of one mole of a substance by one degree Celsius.

• True

• False

If 832 joules of energy are required to raise the temperature of a sample of aluminum from 20.0 °C to 97.0 °C, and the specific heat of aluminum is 0.90 J/(g °C), what is the mass of the aluminum?

• 0.10 g Al

• 10.0 g Al

• 12.0 g Al

• 57.7 g Al

A pan containing 20.0 grams of water was allowed to cool from a temperature of 95.0 °C. The amount of heat released is 1,200 joules. What is the final temperature of the water rounded to the nearest whole number? The specific heat of water is 4.186 J/(g°C).

• 75 °C

• 78 °C

• 81 °C

• 87 °C

CH4(g) + 2O2(g) → CO2(g) + 2H2O(l): ΔH = −890 kJ. Which statement about this reaction is correct?

• The reaction of one mole of oxygen (O2) absorbs 445 kJ of energy.

• The reaction of one mole of oxygen (O2) releases 445 kJ of energy.

• The reaction of one mole of methane (CH4) absorbs 890 kJ of energy.

• The reaction of two moles of methane (CH4) releases 890 kJ of energy.

Which of the following is true about catalysts?

• Catalysts increase the number of collisions that occur between reactants.

• Catalysts increase the activation energy by forming new reactants.

• Catalysts reduce the potential energy of the compounds that are produced.

• Catalysts reduce the energy needed for the reaction to take place.

Which of the following statements explains how temperature affects the rate of a reaction?

• When temperature decreases, collision of particles increases.

• When temperature decreases, kinetic energy increases.

• When temperature increases, particles move slower.

• When temperature increases, particles move faster.

According to Le Châtelier's principle, how will an increase in concentration of a reactant affect the equilibrium system?

• Shift it toward the products

• Shift it toward the reactants

• Shift it toward the side with higher total mole concentration

• Shift it toward the side with lower total mole concentration

Why does the equilibrium of a system shift when the pressure is decreased?

• To maximize the stress on the system

• To stop restoring equilibrium to the system

• To increase the total moles of gas in the system

• To decrease the total moles of gas in the system

Which of the following happens during an exothermic chemical change?

• Heat is absorbed.

• Heat is released.

• Net energy increases.

• Net energy remains constant.

Which of the following happens when a reaction reaches dynamic equilibrium in a closed system?

• Reaction stops.

• Reaction happens in both directions.

• The concentrations of the reactants and products increase.

• The concentrations of the reactants and products decrease.