Q: Millikan’s oil drop experiment determined the charge of a single electron. What is the value of this charge?

$$-1.60 \times 10$$^{-19}$$ \ \mathrm{C}$$

Q: Chlorine has two naturally occurring isotopes: $$^{35}\mathrm{Cl} (34.97 $$amu, 75.77%) and $$^{37}\mathrm{Cl} (36.97 $$amu, 24.23%). What is the atomic mass of chlorine?

$$(34.97 \times 0.7577) + (36.97 \times 0.2423) = 35.45 \ \mathrm{amu}$$

Q: How many atoms are in 2.00 mol of helium?

$$2.00 \times 6.022 \times 10$$^{23}$$ = 1.204 \times 10$$^{24}$$ atoms

Q: A pure platinum ring contains $$3.02 \times 10$$^{22}$$ platinum atoms. How many moles of platinum atoms does it contain?

$$\frac{3.02 \times 10$$^{22}$$}{6.022 \times 10$$^{23}$$} = 0.0501$$ mol

Q: What is the mass in grams of $$2.3 \times 10$$^{-3}$$ mol of antimony (Sb), given that the molar mass of Sb is 121.76 g/mol?

$$2.3 \times 10$$^{-3}$$ \times 121.76 = 0.28 g$$

Question 1

Which statement best describes the Law of Conservation of Mass?

Accepted Answer

The total mass remains constant during a chemical reaction.

Question 2

A sample of water is decomposed into 16.0 g of oxygen and 2.0 g of hydrogen. What is the mass ratio of oxygen to hydrogen in water?

Accepted Answer

$$\frac{16.0}{2.0} = 8.0$$

Question 3

Which law states that all samples of a given compound have the same proportions of their constituent elements?

Accepted Answer

Law of Definite Proportions

Question 4

Carbon dioxide has a mass ratio of oxygen to carbon of 2.67:1, while carbon monoxide has a ratio of 1.33:1. According to the Law of Multiple Proportions, what is the ratio of oxygen in CO$$_2 to CO$$?

Accepted Answer

$$\frac{2.67}{1.33} = 2$$

Question 5

Which of the following is NOT a postulate of Dalton’s Atomic Theory?

Accepted Answer

Atoms are created and destroyed in chemical reactions.

Question 6

J.J. Thomson’s cathode ray experiment led to the discovery of which subatomic particle?

Accepted Answer

Electron

Question 7

Millikan’s oil drop experiment determined the charge of a single electron. What is the value of this charge?

Accepted Answer

$$-1.60 	imes 10$$^{-19}$$ \ \mathrm{C}$$

Question 8

Which experiment disproved the Plum Pudding model and led to the discovery of the atomic nucleus?

Accepted Answer

Rutherford’s Gold Foil Experiment

Question 9

What is the atomic number (Z) of an element?

Accepted Answer

The number of protons in the nucleus

Question 10

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 11

A neutral atom of sodium (Na) has an atomic number of 11. How many electrons does it have?

Accepted Answer

11

Question 12

Which group on the periodic table contains the noble gases?

Accepted Answer

Group 8A

Question 13

Chlorine has two naturally occurring isotopes: $$^{35}\mathrm{Cl} (34.97 $$amu, 75.77%) and $$^{37}\mathrm{Cl} (36.97 $$amu, 24.23%). What is the atomic mass of chlorine?

Accepted Answer

$$(34.97 	imes 0.7577) + (36.97 	imes 0.2423) = 35.45 \ \mathrm{amu}$$

Question 14

How many atoms are in 2.00 mol of helium?

Accepted Answer

$$2.00 	imes 6.022 	imes 10$$^{23}$$ = 1.204 	imes 10$$^{24}$$ atoms

Question 15

A pure platinum ring contains $$3.02 	imes 10$$^{22}$$ platinum atoms. How many moles of platinum atoms does it contain?

Accepted Answer

$$\frac{3.02 	imes 10$$^{22}$$}{6.022 	imes 10$$^{23}$$} = 0.0501$$ mol

Question 16

What is the mass in grams of $$2.3 	imes 10$$^{-3}$$ mol of antimony (Sb), given that the molar mass of Sb is 121.76 g/mol?

Accepted Answer

$$2.3 	imes 10$$^{-3}$$ 	imes 121.76 = 0.28 g$$

Question 17

How many protons, neutrons, and electrons are present in a neutral atom of carbon-14?

Accepted Answer

6 protons, 8 neutrons, 6 electrons

Question 18

Which of the following ions has 13 protons and 10 electrons?

Accepted Answer

$$\mathrm{Al}^{3+}$$

Question 19

A gold bar has dimensions $$8.00 \ \mathrm{cm} 	imes 2.00 \ \mathrm{cm} 	imes 1.50 \ \mathrm{cm}$$ and a density of $$19.3 \ \mathrm{g/cm}^3. $$How many gold atoms are in the bar? (Molar mass of Au = 197.0 g/mol, $$1 \ \mathrm{mol} = 6.022 	imes 10$$^{23}$$ atoms)

Accepted Answer

First, calculate mass: $$8.00 	imes 2.00 	imes 1.50 	imes 19.3 = 463.2 g. $$Moles: $$\frac{463.2}{197.0} = 2.352$$ mol. Atoms: $$2.352 	imes 6.022 	imes 10$$^{23}$$ = 1.42 	imes 10$$^{24}$$ atoms.

Atoms and Elements: Fundamental Laws, Atomic Theory, and Quantitative Relationships

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