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

One mole of any substance contains $$6.022 \times 10$$^{23}$$ entities.

Question 1

Which of the following best describes the concept of significant figures in scientific calculations?

Accepted Answer

Significant figures are the digits in a measurement that are known with certainty plus one estimated digit.

Question 2

A student measures the mass of a sample as 12.30 g and its volume as 4.5 mL. What is the density of the sample, reported with the correct number of significant figures?

Accepted Answer

$$2.7\ \mathrm{g/mL}$$

Question 3

Which of the following statements about the mole is correct?

Accepted Answer

One mole of any substance contains $$6.022 	imes 10$$^{23}$$ entities.

Question 4

How many moles of $$\mathrm{NaCl}$$ are present in $$58.44\ \mathrm{g} of$$ $$\mathrm{NaCl}$$? (Molar mass of $$\mathrm{NaCl} = 58.44\ \mathrm{g/mol})$$

Accepted Answer

$$1.00\ \mathrm{mol}$$

Question 5

A chemical reaction releases $$150.0\ \mathrm{kJ} of $$heat. Which term best describes this reaction?

Accepted Answer

Exothermic

Question 6

Which of the following best explains why water is a good solvent for ionic compounds?

Accepted Answer

Water is a polar molecule, so it can stabilize ions through ion-dipole interactions.

Question 7

Which of the following is the correct electron configuration for a neutral atom of oxygen ($$Z=8$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^4$$

Question 8

A student mixes $$50.0\ \mathrm{mL} of$$ $$1.00\ \mathrm{M}\ \mathrm{HCl}$$ with $$50.0\ \mathrm{mL} of$$ $$1.00\ \mathrm{M}\ \mathrm{NaOH}. $$What is the final concentration of $$\mathrm{NaCl} in $$the resulting solution?

Accepted Answer

$$0.50\ \mathrm{M}$$

Question 9

Which of the following best describes the periodic trend for atomic radius across a period from left to right?

Accepted Answer

Atomic radius decreases due to increasing nuclear charge.

Question 10

Which of the following laboratory safety practices is most important when working with concentrated acids?

Accepted Answer

Always add acid to water, not water to acid.

Question 11

A student is asked to determine the empirical formula of a compound that contains $$40.0\%$$ carbon, $$6.7\%$$ hydrogen, and $$53.3\%$$ oxygen by mass. What is the empirical formula?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 12

Which of the following best describes the process of bomb calorimetry as used in the laboratory?

Accepted Answer

It measures the heat of combustion of a sample at constant volume.

Question 13

Which of the following is a correct balanced equation for the reaction between aqueous sodium sulfate and barium chloride to form a precipitate?

Accepted Answer

$$\mathrm{Na}_2\mathrm{SO}_4\ (aq) + \mathrm{BaCl}_2\ (aq) \rightarrow 2\mathrm{NaCl}\ (aq) + \mathrm{BaSO}_4\ (s)$$

Question 14

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have completely filled valence electron shells.

Question 15

A sample of gas occupies $$2.00\ \mathrm{L} at$$ $$1.00\ \mathrm{atm}$$ and $$300\ \mathrm{K}. If $$the pressure is increased to $$2.00\ \mathrm{atm}$$ and the temperature is increased to $$600\ \mathrm{K}$$, what is the new volume of the gas? (Assume ideal gas behavior.)

Accepted Answer

$$4.00\ \mathrm{L}$$

Question 16

Which of the following is the correct Lewis structure for carbon dioxide ($$\mathrm{CO}_2$$)?

Accepted Answer

O=C=O, with each oxygen atom having two lone pairs.

Question 17

Which of the following best describes the main purpose of a flame test in the laboratory?

Accepted Answer

To identify metal ions based on the color they emit when heated.

Question 18

Which of the following is the correct formula for calculating the enthalpy change ($$\Delta H) of a $$reaction using bond energies?

Accepted Answer

$$\Delta H = \sum 	ext{(bond energies of bonds broken)} - \sum 	ext{(bond energies of bonds formed)}$$

Question 19

A student is asked to prepare $$250\ \mathrm{mL} of$$ $$0.100\ \mathrm{M}$$ $$\mathrm{NaOH}$$ solution from a $$1.00\ \mathrm{M}$$ stock solution. What volume of the stock solution is required?

Accepted Answer

$$25.0\ \mathrm{mL}$$

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