Q: Which of the following is the correct formula for calculating the percent composition of an element in a compound?

$$\frac{\text{mass of element}}{\text{molar mass of compound}} \times 100$$

Question 1

Which of the following best describes the difference between an element and a compound?

Accepted Answer

An element consists of only one type of atom, while a compound consists of two or more types of atoms chemically bonded together.

Question 2

A sample of carbon contains two isotopes: $$^{12}C (98.93$$%) and $$^{13}C (1.07$$%). What is the average atomic mass of carbon?

Accepted Answer

$$12.01\ \mathrm{amu}$$

Question 3

Which of the following is the correct electron configuration for $$\mathrm{Fe$$^{2+}$$}$$?

Accepted Answer

$$[Ar]\ 3d^6$

Question 4

Which statement best explains why $$\mathrm{Mg}$$ has a higher ionization energy than $$\mathrm{Na}$$?

Accepted Answer

Magnesium has a smaller atomic radius and a greater effective nuclear charge than sodium.

Question 5

A student collects hydrogen gas over water at $$25^\circ\mathrm{C}$$ and a total pressure of $$755\ \mathrm{mmHg}. $$The vapor pressure of water at $$25^\circ\mathrm{C} is$$ $$23.8\ \mathrm{mmHg}. $$What is the pressure of the hydrogen gas?

Accepted Answer

$$731.2\ \mathrm{mmHg}$$

Question 6

Which of the following best describes the Maxwell-Boltzmann distribution for a gas at higher temperature?

Accepted Answer

The distribution shifts to higher speeds and becomes broader.

Question 7

Which compound will precipitate when solutions of $$\mathrm{$$AgNO_3$$}$$ and $$\mathrm{NaCl}$$ are mixed?

Accepted Answer

$$\mathrm{AgCl}$$

Question 8

Which of the following is the correct empirical formula for a compound containing 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 9

Which of the following best explains why $$\mathrm{O_2$} is $$paramagnetic?

Accepted Answer

It has unpaired electrons in its antibonding molecular orbitals.

Question 10

Which of the following statements about hydrogen bonding is correct?

Accepted Answer

Hydrogen bonding is responsible for the high boiling point of water.

Question 11

A solution is prepared by dissolving $$5.00\ \mathrm{g} of$$ $$\mathrm{NaCl} in$$ $$100.0\ \mathrm{g} of $$water. What is the molality of the solution?

Accepted Answer

$$0.855\ \mathrm{mol/kg}$$

Question 12

Which of the following best describes the relationship between boiling point and intermolecular forces?

Accepted Answer

Boiling point increases as intermolecular forces increase.

Question 13

Which of the following is the correct formula for calculating the energy of a photon?

Accepted Answer

$$E = h
u$$

Question 14

Which of the following is a correct statement about the dual nature of light?

Accepted Answer

Light exhibits both wave-like and particle-like properties.

Question 15

Which of the following best explains why $$\mathrm{F_2$}$$ has a lower boiling point than $$\mathrm{Cl_2$}$$?

Accepted Answer

$$\mathrm{F_2$}$$ has weaker London dispersion forces due to its smaller size.

Question 16

Which of the following is the correct formula for calculating the molar volume of a gas at STP?

Accepted Answer

$$22.4\ \mathrm{L/mol}$$

Question 17

Which of the following is the correct formula for calculating the percent composition of an element in a compound?

Accepted Answer

$$\frac{	ext{mass of element}}{	ext{molar mass of compound}} 	imes 100$$

Question 18

Which of the following best describes the effect of increasing temperature on the solubility of most solid solutes in water?

Accepted Answer

Solubility increases as temperature increases.

Question 19

Which of the following is the correct formula for the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 20

Which of the following best explains why ionic compounds tend to have high melting points?

Accepted Answer

Ionic compounds have strong electrostatic attractions between oppositely charged ions.

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