Q: A railroad spike weighs $$1.1\ \mathrm{kg}. $$How many moles of iron atoms does it contain? (Molar mass of Fe = $$55.845\ \mathrm{g/mol})$$

$$\frac{1.1\ \mathrm{kg} \times 1000\ \mathrm{g/kg}}{55.845\ \mathrm{g/mol}} = 20\ \mathrm{mol}$$

Question 1

Which of the following best describes the difference between precision and accuracy in scientific measurements?

Accepted Answer

Precision refers to how close measured values are to each other, while accuracy refers to how close measured values are to the true value.

Question 2

A granite block has a mass of 78 g. If the density of granite is $$2.6\ \mathrm{g/cm^3$}$$, what is the volume of the block in $$\mathrm{cm^3$}$$?

Accepted Answer

$$v = \frac{m}{D} = \frac{78\ \mathrm{g}}{2.6\ \mathrm{g/cm^3$}} = 30\ \mathrm{cm^3$}$$

Question 3

Which of the following is an example of a chemical change?

Accepted Answer

Burning a match

Question 4

A sample of methane is analyzed by mass spectrometry and shows a small peak at $$17\ \mathrm{m/z} in $$addition to the main peak at $$16\ \mathrm{m/z}. $$What is the most likely explanation for the $$17\ \mathrm{m/z}$$ peak?

Accepted Answer

The presence of $$^{13}\mathrm{C}$$ isotope in some methane molecules

Question 5

Which law is illustrated by the fact that every specimen of methane contains $$12\ \mathrm{g} of $$carbon for every $$4\ \mathrm{g} of $$hydrogen?

Accepted Answer

Law of definite proportions

Question 6

A compound is made from a metal and a nonmetal. Which type of compound is it most likely to be?

Accepted Answer

Ionic

Question 7

Which of the following scientists is correctly matched with their major contribution?

Accepted Answer

Rutherford — discovered the atomic nucleus

Question 8

A railroad spike weighs $$1.1\ \mathrm{kg}. $$How many moles of iron atoms does it contain? (Molar mass of Fe = $$55.845\ \mathrm{g/mol})$$

Accepted Answer

$$\frac{1.1\ \mathrm{kg} 	imes 1000\ \mathrm{g/kg}}{55.845\ \mathrm{g/mol}} = 20\ \mathrm{mol}$$

Question 9

Which of the following is the correct name for the compound $$\mathrm{V_2O_5}$$?

Accepted Answer

Vanadium (V) oxide

Question 10

If a compound is made from two nonmetals, it is most likely to be:

Accepted Answer

Molecular

Question 11

What is the empirical formula of a hydrocarbon that produces $$2.81\ \mathrm{g} of$$ $$\mathrm{CO_2$}$$ and $$0.576\ \mathrm{g} of$$ $$\mathrm{H_2O}$$ upon complete combustion?

Accepted Answer

CH

Question 12

Which of the following best describes the difference between a theory and a law in science?

Accepted Answer

A law identifies a pattern in scientific observations, while a theory explains why the pattern exists.

Question 13

A sample of chlorine contains two isotopes: $$^{35}\mathrm{Cl} ($$mass = $$34.96885\ \mathrm{amu}) $$and $$^{37}\mathrm{Cl} ($$mass = $$36.96590\ \mathrm{amu}). If $$the average atomic mass is $$35.453\ \mathrm{amu}$$, what is the percent abundance of $$^{35}\mathrm{Cl}$$?

Accepted Answer

75.8%

Question 14

What is the correct formula and name for the compound formed from strontium and sulfur?

Accepted Answer

SrS, strontium sulfide

Question 15

Which of the following ions is correctly named?

Accepted Answer

$$AsO_3$$^{3-} is arsenite

Question 16

What is the molecular weight of acetic acid ($$\mathrm{C_2H_4O_2}$$)? (C = $$12.011\ \mathrm{g/mol}$$, H = $$1.00794\ \mathrm{g/mol}$$, O = $$15.9994\ \mathrm{g/mol})$$

Accepted Answer

$$60.05\ \mathrm{g/mol}$$

Question 17

Which of the following is the correct name for $$\mathrm{Cl_2O_7}$$?

Accepted Answer

Dichlorine heptoxide

Question 18

Which of the following best describes the law of multiple proportions?

Accepted Answer

When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in the ratio of small whole numbers.

Question 19

Which of the following is the correct percent by mass of carbon in acetic acid ($$\mathrm{C_2H_4O_2}$$)?

Accepted Answer

40%

Question 20

Which of the following is the correct name for the acid formed when $$\mathrm{HI}$$ dissolves in water?

Accepted Answer

Hydroiodic acid

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