Q: Which of the following is a correct balanced equation for the reaction of aluminum with hydrochloric acid?

$$2\text{Al} + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2$$

Q: Which of the following is a double replacement reaction?

$$\text{AB} + \text{CD} \rightarrow \text{AD} + \text{CB}$$

Question 1

A 100.0 g sample of a radioactive isotope decays to 12.5 g after 3 half-lives. What is the half-life if the total elapsed time is 24 hours?

Accepted Answer

$$8\ 	ext{hours}$$

Question 2

Which of the following best describes why NH$$_3 is $$highly soluble in water?

Accepted Answer

NH$$_3$$ can form hydrogen bonds with water molecules.

Question 3

A student measures the mass of a metal cylinder as $$12.34\ 	ext{g}$$ and its volume as $$4.56\ 	ext{cm}^3. $$What is the density of the cylinder, reported with the correct number of significant figures?

Accepted Answer

$$2.7\ 	ext{g/cm}^3$$

Question 4

Which of the following is the correct electron configuration for a chloride ion (Cl$$^-$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$

Question 5

A solution is prepared by dissolving $$25.0\ 	ext{g} of $$NaCl in enough water to make $$500.0\ 	ext{mL} of $$solution. What is the molarity of the solution? (Molar mass of NaCl = $$58.44\ 	ext{g/mol})$$

Accepted Answer

$$0.856\ 	ext{M}$$

Question 6

Which of the following statements about the solubility of gases in water is correct?

Accepted Answer

The solubility increases with increasing pressure and decreases with increasing temperature.

Question 7

A sample of gas occupies $$2.50\ 	ext{L} at$$ $$1.00\ 	ext{atm}$$ and $$25^\circ	ext{C}. $$What volume will it occupy at $$2.00\ 	ext{atm}$$ and $$25^\circ	ext{C}$$?

Accepted Answer

$$1.25\ 	ext{L}$$

Question 8

Which of the following compounds contains a polar covalent bond?

Accepted Answer

HCl

Question 9

A compound has an empirical formula of CH$$_2O $$and a molar mass of $$180\ 	ext{g/mol}. $$What is its molecular formula?

Accepted Answer

C$$_6H$_{12}O$_6$$

Question 10

Which of the following best describes the geometry of SO$$_2$$?

Accepted Answer

Bent due to the presence of a lone pair on the central atom.

Question 11

Which of the following is a correct balanced equation for the reaction of aluminum with hydrochloric acid?

Accepted Answer

$$2	ext{Al} + 6	ext{HCl} ightarrow 2	ext{AlCl}_3 + 3	ext{H}_2$$

Question 12

Which of the following is NOT a property of acids?

Accepted Answer

Turns litmus blue

Question 13

A sample of $$0.225$$ mole of gas has a volume of $$748\ 	ext{mL} at$$ $$28^\circ	ext{C}. $$Calculate the pressure in atm using $$R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}.$$

Accepted Answer

$$7.43\ 	ext{atm}$$

Question 14

Which of the following is the correct name for the compound with the formula $$	ext{Ca(ClO}_3)_2$$?

Accepted Answer

Calcium chlorate

Question 15

Which of the following best explains why Cl$$_2 is a $$nonpolar molecule?

Accepted Answer

It is a diatomic molecule with identical atoms sharing electrons equally.

Question 16

Which of the following is the correct formula for ammonium hydrogen carbonate?

Accepted Answer

$$	ext{NH}_4	ext{HCO}_3$$

Question 17

Which of the following is a double replacement reaction?

Accepted Answer

$$	ext{AB} + 	ext{CD} ightarrow 	ext{AD} + 	ext{CB}$$

Question 18

A lead ball has a mass of $$75.0\ 	ext{g}$$ and a density of $$11.4\ 	ext{g/cm}^3. $$What is the volume of the ball?

Accepted Answer

$$6.58\ 	ext{cm}^3$$

Question 19

Which of the following best describes the role of spectator ions in a precipitation reaction?

Accepted Answer

They are unchanged and remain in solution.

Question 20

Which of the following molecules exhibits hydrogen bonding?

Accepted Answer

NH$$_3$$

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