Q: If you have $$0.240$$ mol of sodium ($$Na$$), how many sodium atoms do you have? ($$1$$ mol $$Na = 6.02 \times 10$$^{23}$$ atoms)

$$1.44 \times 10$$^{23}$$ atoms

Question 1

Which of the following best describes the Law of Conservation of Mass as established by Antoine Lavoisier?

Accepted Answer

The total mass of substances present before a chemical reaction is equal to the total mass after the reaction.

Question 2

The term 'atom' comes from the Greek word 'atomos,' which means:

Accepted Answer

cannot be cut

Question 3

A log is burned in a campfire and the mass of the ash is much less than the mass of the original log. According to the law of conservation of mass, what happened to the matter?

Accepted Answer

The matter that composed the log reacts to form gases that are released into the air.

Question 4

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

Accepted Answer

Atoms can be created or destroyed in chemical reactions.

Question 5

Which chemical law is illustrated by the following data: Compound A contains 1.333 g of oxygen per gram of carbon, whereas compound B contains 2.666 g of oxygen per gram of carbon?

Accepted Answer

The law of multiple proportions

Question 6

If compound A has an equal number of oxygen and carbon atoms, and compound B contains twice as much oxygen per gram of carbon, what can we conclude about compound B?

Accepted Answer

The second compound must have twice as many oxygen atoms per carbon atom as the first compound.

Question 7

Which statement best captures the difference between the law of definite proportions and the law of multiple proportions?

Accepted Answer

The law of definite proportions applies to two or more samples of the same compound, while the law of multiple proportions applies to two different compounds containing the same two elements.

Question 8

Which of the following best describes how Mendeleev arranged the elements in his early periodic table?

Accepted Answer

By similar chemical properties

Question 9

Avogadro’s number is used to convert between which two quantities?

Accepted Answer

Moles and particles

Question 10

How many moles of $$CO_2$$ are in $$2.50 	imes 10$$^{24}$$ molecules of CO_2$? Use 6.02$$ 	imes $$10^{23} as $$Avogadro’s number.

Accepted Answer

$$4.15$$ moles

Question 11

What is the mass, in grams, of $$3.25$$ moles of ammonia, $$NH_3$$? (Molar mass of $$NH_3 = 17.03$ g/mol)

Accepted Answer

$$55.3 g$$

Question 12

A pure copper penny contains $$2.81 	imes 10$$^{22}$$ atoms of copper. What is its mass? (Molar mass of Cu = 63.55$ g/mol, Avogadro’s number = 6.02$$ 	imes $$10^{23})$$

Accepted Answer

$$2.97 g$$

Question 13

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 14

Which of the following is true for 1 mole of carbon?

Accepted Answer

All of the above

Question 15

Which of the following is an example of green chemistry?

Accepted Answer

Replacing mercury fluorescent light bulbs with efficient mercury-free light bulbs.

Question 16

If you have $$0.240$$ mol of sodium ($$Na$$), how many sodium atoms do you have? ($$1$$ mol $$Na = 6.02 	imes 10$$^{23}$$ atoms)

Accepted Answer

$$1.44 	imes 10$$^{23}$$ atoms

Question 17

Which has more atoms: $$10.0 g of$$ $$Mg or$$ $$10.0 g of$$ $$Ca$$? (Atomic masses: $$Mg = 24.31 g/$$mol, $$Ca = 40.08 g/$$mol)

Accepted Answer

Magnesium

Question 18

Which of the following best explains why carbon monoxide ($$CO) is $$dangerous to humans?

Accepted Answer

It binds tightly to hemoglobin, preventing oxygen transport in the blood.

Question 19

Which of the following reactions is consistent with Dalton’s Atomic Theory?

Accepted Answer

$$C + H_2$ \rightarrow CH_4$

Atoms, Atomic Theory, and the Periodic Table: Study Notes for Introductory Chemistry

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