Question 1

A steam locomotive uses a firebox to heat water and produce steam, which then moves the train. Which of the following best describes the energy transformations occurring in the firebox?

Accepted Answer

Chemical energy in the fuel is converted to thermal energy, which is then converted to kinetic energy.

Question 2

Which of the following equations correctly represents the calculation of kinetic energy for an object of mass $$m$$ moving at velocity $$v$$?

Accepted Answer

$$E_k = \frac{1}{2} m v^2$

Question 3

A 10 kg weight is dropped from the top of a building. Which type of energy transformation occurs as the weight falls and hits the ground?

Accepted Answer

Potential energy is converted to kinetic energy, then to thermal energy upon impact.

Question 4

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

Accepted Answer

Energy is neither created nor destroyed; it can only be transferred or transformed.

Question 5

A chemical cold pack is activated and absorbs heat from its surroundings. Which of the following best describes this process?

Accepted Answer

It is an endothermic process with $$\Delta H \u003e 0.$$

Question 6

Which of the following is the correct expression for the change in internal energy ($$\Delta E) of a $$system?

Accepted Answer

$$\Delta E = q + w$$

Question 7

A gas expands against a constant external pressure, doing work on the surroundings. Which equation correctly describes the work done by the gas?

Accepted Answer

$$w = -P \Delta V$$

Question 8

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 9

A reaction occurs in an open beaker at constant pressure and releases heat to the surroundings. Which of the following statements is true?

Accepted Answer

$$\Delta H \u003c 0$$, the reaction is exothermic.

Question 10

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

Accepted Answer

Heat is energy transfer due to temperature difference; work is energy transfer due to force acting over a distance.

Question 11

A battery is discharged by running a fan and by short-circuiting it. In both cases, the change in internal energy ($$\Delta E) is $$the same, but the values of $$q$$ and $$w$$ are different. What does this demonstrate?

Accepted Answer

$$q$$ and $$w$$ are not state functions, but $$\Delta E is.$$

Question 12

Which of the following correctly describes the sign conventions for $$q$$, $$w$$, and $$\Delta E$$?

Accepted Answer

$$\Delta E \u003e 0$$ means net gain of energy by the system.

Question 13

A solution contains magnesium chloride. When excess potassium carbonate is added, a white precipitate forms. What is the net ionic equation for this reaction?

Accepted Answer

$$\mathrm{Mg$$^{2+}$$(aq) + CO_3$^{2-}(aq) \rightarrow $$MgCO_3$$(s)}$$

Question 14

Which of the following best describes an exothermic reaction?

Accepted Answer

Heat flows from the system into the surroundings.

Question 15

Which of the following is the correct formula for electrostatic potential energy between two charges $$Q_1$$ and $$Q_2$$ separated by distance $$d$$?

Accepted Answer

$$E_{el} = k \frac{Q_1$ Q_2$}{d}$$

Question 16

A student burns 25 food calories during exercise. How many joules is this equivalent to? (1 food Calorie = 1 kcal, 1 cal = 4.184 J)

Accepted Answer

$$25 	imes 1000 	imes 4.184 = 104,600 J$$

Question 17

Which of the following best describes the relationship between temperature and the average kinetic energy of gas molecules?

Accepted Answer

Higher temperature means higher average kinetic energy.

Question 18

Which of the following is true about enthalpy ($$H) $$and its change ($$\Delta H) at $$constant pressure?

Accepted Answer

$$\Delta H$$ equals the heat exchanged at constant pressure.

Question 19

Which of the following best describes a state function?

Accepted Answer

A property that depends only on the current state of the system, not on how it got there.

Thermochemistry and Energy in Chemical Systems: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard