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

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

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? ($$	ext{MgCO}_3$$ molar mass = 84.3 g/mol)

Accepted Answer

$$0.50\ 	ext{M}$$

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

$$	ext{Mg}^{2+}(aq) + 	ext{CO}_3$$^{2-}$$(aq) ightarrow 	ext{MgCO}_3(s)$$

Question 4

Which of the following statements about oxidation numbers is correct for $$	ext{MnO}_4^-$$?

Accepted Answer

Mn: $$+7$$, O: $$-2$$

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 equations correctly expresses the relationship between internal energy, heat, and work?

Accepted Answer

$$\Delta E = q + w$$

Question 7

A gas expands against a constant external pressure of 1.00 atm, increasing its volume by 2.00 L. What is the work done by the system? ($$1\ 	ext{L} \cdot 	ext{atm} = 101.3\ 	ext{J})$$

Accepted Answer

$$-202.6\ 	ext{J}$$

Question 8

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 9

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 10

Which of the following best describes the sign conventions for $$q$$, $$w$$, and $$\Delta E$$ when a system absorbs heat and work is done on the system?

Accepted Answer

$$q \u003e 0$$, $$w \u003e 0$$, $$\Delta E \u003e 0$$

Question 11

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 12

Which of the following statements about enthalpy ($$H) is $$correct?

Accepted Answer

Enthalpy is the sum of internal energy and the product of pressure and volume: $$H = E + PV.$$

Question 13

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

Accepted Answer

$$\Delta H \u003c 0$$, $$q \u003c 0$$

Question 14

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

Accepted Answer

Heat is energy transferred due to temperature difference; work is energy transferred by force acting through a distance.

Question 15

Which of the following processes is exothermic?

Accepted Answer

Combustion of gasoline in an engine

Question 16

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

Accepted Answer

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

Question 17

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.

Question 18

Which of the following is the correct expression for pressure-volume work?

Accepted Answer

$$w = -P\Delta V$$

Question 19

Which of the following is true about the first law of thermodynamics?

Accepted Answer

The total energy of the universe is constant.

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