Q: Which of the following statements about the mole is correct?

A mole contains $$6.022 \times 10$$^{23}$$ particles of a substance.

Question 1

Which of the following is the correct balanced chemical equation for the combustion of propane ($$\mathrm{C_3H_8}) in $$oxygen?

Accepted Answer

$$\mathrm{C_3H_8} + 5\ \mathrm{O_2$} \rightarrow 3\ \mathrm{CO_2$} + 4\ \mathrm{H_2O}$$

Question 2

Which of the following best describes a double displacement (metathesis) reaction?

Accepted Answer

Two compounds exchange ions to form two new compounds.

Question 3

Which of the following statements about the mole is correct?

Accepted Answer

A mole contains $$6.022 	imes 10$$^{23}$$ particles of a substance.

Question 4

How many molecules are present in 0.25 moles of $$\mathrm{CO_2$}$$? (Use Avogadro’s number: $$6.022 	imes 10$$^{23}$$)

Accepted Answer

$$1.51 	imes 10$$^{23}$$

Question 5

What is the molar mass of $$\mathrm{Ca(NO_3$)_2}$$?

Accepted Answer

$$164\ \mathrm{g/mol}$$

Question 6

Given the reaction: $$2\ \mathrm{Al} + 3\ \mathrm{Cl_2$} \rightarrow 2\ \mathrm{$$AlCl_3$$}$$, how many moles of $$\mathrm{Cl_2$}$$ are needed to react completely with 5 moles of $$\mathrm{Al}$$?

Accepted Answer

$$7.5$$ moles

Question 7

A student reacts 10.0 g of $$\mathrm{H_2$}$$ with excess $$\mathrm{O_2$} to $$produce water. The theoretical yield is 89.4 g, but only 80.0 g is collected. What is the percent yield?

Accepted Answer

$$89.5\%$$

Question 8

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

Accepted Answer

A negative $$\Delta H$$ indicates an exothermic reaction.

Question 9

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It lowers the activation energy, increasing the reaction rate.

Question 10

Given the equilibrium: $$\mathrm{N_2$} + 3\ \mathrm{H_2$} \rightleftharpoons 2\ \mathrm{NH_3$}$$, which is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \dfrac{[\mathrm{NH_3$}]^2}{[\mathrm{N_2$}][\mathrm{H_2$}]^3}$$

Question 11

Which of the following gases will have the highest rate of effusion at the same temperature and pressure?

Accepted Answer

$$\mathrm{H_2$}$$

Question 12

A 2.00 L sample of gas at 1.00 atm and 300 K is compressed to 1.00 L at constant temperature. What is the final pressure?

Accepted Answer

$$2.00$$ atm

Question 13

Which intermolecular force is primarily responsible for the high boiling point of water?

Accepted Answer

Hydrogen bonding

Question 14

Which of the following solutions is the best example of a strong electrolyte?

Accepted Answer

$$\mathrm{NaCl} (aq)$$

Question 15

What is the molarity of a solution prepared by dissolving 10.0 g of $$\mathrm{NaOH} ($$molar mass = $$40.0\ \mathrm{g/mol}) in $$enough water to make $$500.0\ \mathrm{mL} of $$solution?

Accepted Answer

$$0.50\ \mathrm{M}$$

Question 16

Which of the following is the correct neutralization reaction between $$\mathrm{H_2SO_4}$$ and $$\mathrm{KOH}$$?

Accepted Answer

$$\mathrm{H_2SO_4} + 2\ \mathrm{KOH} \rightarrow 2\ \mathrm{H_2O} + \mathrm{K_2SO_4}$$

Question 17

A buffer solution can be made by mixing:

Accepted Answer

A weak acid and its conjugate base

Question 18

What is the pH of a solution with $$[\mathrm{H^+}] = 1.0 	imes 10$$^{-4}$$\ \mathrm{M}$$?

Accepted Answer

4.00

Question 19

Which of the following changes will increase the solubility of a gas in water?

Accepted Answer

Decreasing the temperature and increasing the pressure

Question 20

A solution is prepared by mixing 25.0 mL of ethanol with enough water to make 100.0 mL of solution. What is the $$\mathrm{v/v\%} of $$ethanol?

Accepted Answer

$$25.0\%$$

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