Question 1

A 500 mL solution of magnesium chloride reacts with excess potassium carbonate to form 21 g of a white precipitate. What is the molarity of magnesium chloride in the original solution? (Molar mass of MgCO$$_3 = 84.3 g/$$mol)

Accepted Answer

$$0.50\ \mathrm{M}$$

Question 2

Which of the following best describes the energy transformation in a steam locomotive firebox (as shown in the image)?

Accepted Answer

Chemical energy is converted to thermal energy.

Question 3

Which of the following is the correct balanced net ionic equation for the precipitation reaction between magnesium chloride and potassium carbonate?

Accepted Answer

$$\mathrm{Mg}^{2+}(aq) + \mathrm{CO}_3$$^{2-}$$(aq) \rightarrow \mathrm{MgCO}_3(s)$$

Question 4

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

Accepted Answer

The total energy of the universe is constant.

Question 5

A cyclist coasts down a hill, converting potential energy to kinetic energy. If friction is present, what additional energy transformation occurs?

Accepted Answer

Kinetic energy is converted to thermal energy.

Question 6

Which of the following is the correct formula for the kinetic energy of an object?

Accepted Answer

$$E_k = \frac{1}{2}mv^2$

Question 7

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 8

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 9

If a system does 150 J of work on the surroundings and absorbs 200 J of heat, what is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = 50\ \mathrm{J}$$

Question 10

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

Accepted Answer

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

Question 11

Which equation correctly relates the change in internal energy to heat and work?

Accepted Answer

$$\Delta E = q + w$$

Question 12

A gas expands against a constant external pressure of 2.0 atm, increasing its volume by 3.0 L. What is the work done by the system? (1 L·atm = 101.3 J)

Accepted Answer

$$-608\ \mathrm{J}$$

Question 13

Which of the following best describes an exothermic reaction?

Accepted Answer

$$\Delta H \u003c 0$$, heat is released to the surroundings

Question 14

Which of the following is the correct expression for enthalpy ($$H$$)?

Accepted Answer

$$H = E + PV$$

Question 15

A student burns 25 food 'calories' (1 food Calorie = 1 kcal) during a workout. How many joules is this?

Accepted Answer

$$104,600\ \mathrm{J}$$

Question 16

Which of the following best describes the energy change when a weight is dropped from a building and comes to rest on the ground?

Accepted Answer

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

Question 17

Which of the following is true about heat ($$q) $$and work ($$w) as $$state functions?

Accepted Answer

Neither $$q$$ nor $$w is a $$state function.

Question 18

Which of the following best describes the process when an MRE heater is activated?

Accepted Answer

An exothermic chemical reaction releases heat.

Question 19

Which of the following is the correct formula for electrostatic potential energy between two charges?

Accepted Answer

$$E_{el} = k\frac{Q_1Q_2}{d}$$

Thermochemistry and Energy in Chemical Systems: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard