Q: Which of the following is the correct formula for calculating the heat absorbed or released by a substance?

$$q = m \times C_s \times \Delta T$$

Question 1

A 10 kg object is dropped from a height of 20 m. Ignoring air resistance, what is the kinetic energy of the object just before it hits the ground? (Take $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$1960 \ \mathrm{J}$$

Question 2

Which of the following best describes the difference between heat and work in thermodynamics?

Accepted Answer

Work is the result of a force acting through a distance, while heat is the flow of energy caused by a temperature change.

Question 3

A chemical reaction in a beaker feels cold to the touch. Which of the following statements is true about the reaction?

Accepted Answer

The reaction is endothermic and $$\Delta H is $$positive.

Question 4

Which equation correctly expresses the relationship between the change in internal energy, heat, and work?

Accepted Answer

$$\Delta E = q + w$$

Question 5

A 50.0 g sample of metal at $$100.0\ ^\circ\mathrm{C} is $$placed in 100.0 g of water at $$25.0\ ^\circ\mathrm{C}. If $$the final temperature is $$30.0\ ^\circ\mathrm{C}$$, what is the specific heat capacity of the metal? ($$c_{\mathrm{water}} = 4.18\ \mathrm{J/g\ ^\circ C})$$

Accepted Answer

$$0.60\ \mathrm{J/g\ ^\circ C}$$

Question 6

Which of the following is a state function?

Accepted Answer

Internal energy

Question 7

A gas expands against a constant external pressure of $$2.00\ \mathrm{atm}$$ from $$5.00\ \mathrm{L} to$$ $$10.00\ \mathrm{L}. $$What is the work done by the gas? ($$1\ \mathrm{L\ atm} = 101.3\ \mathrm{J})$$

Accepted Answer

$$-1013\ \mathrm{J}$$

Question 8

Which of the following best describes the energy changes when a ball rolls across a rough table and comes to a stop?

Accepted Answer

Kinetic energy is converted to heat due to friction.

Question 9

Which of the following statements about the first law of thermodynamics is correct?

Accepted Answer

The total energy of the universe is constant.

Question 10

A reaction has $$\Delta H = -250\ \mathrm{kJ}. $$Which of the following is true?

Accepted Answer

The reaction is exothermic and releases heat.

Question 11

Which of the following is the correct formula for calculating the heat absorbed or released by a substance?

Accepted Answer

$$q = m 	imes C_s 	imes \Delta T$$

Question 12

If the internal energy of a system decreases by 150 J while it does 50 J of work on the surroundings, how much heat was transferred?

Accepted Answer

$$-100\ \mathrm{J}$$

Question 13

Which of the following best describes the energy transfer in an instant cold pack applied to an injury?

Accepted Answer

Heat flows from the surroundings into the cold pack.

Question 14

Which of the following is true for an exothermic reaction?

Accepted Answer

The products have lower chemical potential energy than the reactants.

Question 15

A reaction is carried out in a bomb calorimeter and the temperature of the water increases. What can be concluded about the reaction?

Accepted Answer

The reaction is exothermic.

Question 16

Which of the following is NOT a correct unit for energy?

Accepted Answer

Newton (N)

Question 17

Which of the following best describes a state function?

Accepted Answer

A property that depends only on the initial and final states, not on the path taken.

Question 18

Which of the following equations correctly relates the enthalpy change of a reaction to the enthalpies of formation of the products and reactants?

Accepted Answer

$$\Delta H_{\mathrm{rxn}} = \sum n \Delta H_f$$^{\circ}$$ (\mathrm{products}) - \sum n \Delta H_f$$^{\circ}$$ (\mathrm{reactants})$$

Thermochemistry: Energy, Heat, and Work in Chemical Systems

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