Q: How many atoms are present in $$2.5$$ moles of carbon dioxide ($$CO_2$$)?

$$2.5 \times 3 \times 6.022 \times 10$$^{23}$$

Q: Calculate the mass in grams of one carbon-12 atom using the atomic mass unit ($$1\text{ amu} = 1.66054 \times 10$$^{-24}$$\text{ g}).$$

$$1.9926 \times 10$$^{-23}$$\text{ g}$$

Q: A sample contains $$3.0$$ moles of sodium atoms. What is the total number of sodium atoms in the sample?

$$3.0 \times 6.022 \times 10$$^{23}$$

Q: Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

$$\text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}$$

Question 1

Which of the following statements about the modern view of atomic structure is FALSE?

Accepted Answer

The number of protons and neutrons in the nucleus is roughly equal.

Question 2

Which of the following pairs of elements would you expect to have the most similar chemical properties?

Accepted Answer

Oxygen (O) and Sulfur (S)

Question 3

A sample of $$^{13}C ($$carbon-13) has an atomic number of 6 and a mass number of 13. How many neutrons does it contain?

Accepted Answer

$$7$$

Question 4

Which of the following represents a pair of isotopes?

Accepted Answer

$$^{12}C$$ and $$^{14}C$$

Question 5

Lithium exists as two major isotopes: lithium-6 and lithium-7. Given that the atomic mass of lithium is $$6.94$$ amu, which isotope is more abundant?

Accepted Answer

Lithium-7

Question 6

The water used for nuclear reactors is sometimes enriched with a mixture of $$^{1}H_2O$$ and $$^{2}H_2O ($$heavy water). If the natural abundance of $$^{2}H is$$ $$0.015	ext{\%}$$, what is the ratio of $$^{2}H$$ atoms to $$^{1}H$$ atoms in natural water?

Accepted Answer

$$1.5 	imes 10$$^{-4}$$

Question 7

How many atoms are present in $$2.5$$ moles of carbon dioxide ($$CO_2$$)?

Accepted Answer

$$2.5 	imes 3 	imes 6.022 	imes 10$$^{23}$$

Question 8

Calculate the mass in grams of one carbon-12 atom using the atomic mass unit ($$1	ext{ amu} = 1.66054 	imes 10$$^{-24}$$	ext{ g}).$$

Accepted Answer

$$1.9926 	imes 10$$^{-23}$$	ext{ g}$$

Question 9

A sample contains $$3.0$$ moles of sodium atoms. What is the total number of sodium atoms in the sample?

Accepted Answer

$$3.0 	imes 6.022 	imes 10$$^{23}$$

Question 10

Determine the mass in grams of $$2.0$$ moles of $$^{24}Mg$$ atoms. ($$1$$ mole $$^{24}Mg$$ = $$24.0 g)$$

Accepted Answer

$$48.0 g$$

Question 11

If you have $$1.0 g of$$ $$^{12}C$$, how many atoms of $$^{12}C$$ are present? ($$1$$ mole $$^{12}C$$ = $$12.0 g)$$

Accepted Answer

$$5.02 	imes 10$$^{22}$$

Question 12

A compound contains $$2.41 g of $$sodium and $$5.48 g of $$sulfur. What is the empirical formula of the compound?

Accepted Answer

$$Na_2S$$

Question 13

Which of the following best describes isotopes?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 14

A sample of chlorine contains $$75.77\%$$ $$^{35}Cl$$ and $$24.23\%$$ $$^{37}Cl. $$What is the average atomic mass of chlorine?

Accepted Answer

$$35.48$$ amu

Question 15

Which of the following statements is TRUE about the periodic table?

Accepted Answer

Elements in the same group have similar chemical properties.

Question 16

If you have $$0.5$$ moles of $$CO_2$$, how many $$CO_2$$ molecules are present?

Accepted Answer

$$3.011 	imes 10$$^{23}$$

Question 17

Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

Accepted Answer

$$	ext{moles} = \frac{	ext{mass (g)}}{	ext{molar mass (g/mol)}}$$

Question 18

A sample contains $$1.5 	imes 10$$^{24}$$ atoms of iron. How many moles of iron are present?

Accepted Answer

$$2.49$$ moles

Question 19

Which of the following is the correct relationship between atomic number ($$Z$$), mass number ($$A$$), and number of neutrons ($$N$$)?

Accepted Answer

$$N = A - Z$$

Atoms, Isotopes, and Atomic Mass: General Chemistry Study Notes (Worksheet Review)

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