Q: Which of the following statements about Avogadro’s number is correct?

Avogadro’s number is $$6.02 \times 10$$^{23}$$ and represents the number of particles in one mole of a substance.

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 after a chemical reaction is equal to the mass before the reaction.

Question 2

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

Accepted Answer

cannot be cut

Question 3

A log burns completely 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

After a 10 g sample of lithium metal reacts in a closed container with 44.32 g of chlorine gas, 1.32 g of lithium remains and all the chlorine is consumed. What mass of lithium chloride is formed?

Accepted Answer

$$54.32\ \mathrm{g}$$

Question 5

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 6

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 7

Compound A contains $$1.333\ \mathrm{g} of $$oxygen per gram of carbon, whereas compound B contains $$2.666\ \mathrm{g} of $$oxygen per gram of carbon. What chemical law do these data illustrate?

Accepted Answer

The law of multiple proportions

Question 8

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

Accepted Answer

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

Question 9

In his early periodic table, Mendeleev arranged the known elements into groups primarily according to what criterion?

Accepted Answer

Similar chemical properties

Question 10

Which of the following statements about Avogadro’s number is correct?

Accepted Answer

Avogadro’s number is $$6.02 	imes 10$$^{23}$$ and represents the number of particles in one mole of a substance.

Question 11

How many moles of $$\mathrm{CO}_2$$ are in $$2.50 	imes 10$$^{24}$$ molecules of $$\mathrm{CO}_2$$?

Accepted Answer

$$4.15$$ moles

Question 12

What is the mass, in grams, of $$3.25$$ moles of ammonia, $$\mathrm{NH}_3$$? (Molar mass of $$\mathrm{NH}_3 is$$ $$17.03\ \mathrm{g/mol})$$

Accepted Answer

$$55.3\ \mathrm{g}$$

Question 13

Which of the following is true about isotopes?

Accepted Answer

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

Question 14

Which of the following is correct?

Accepted Answer

All of the above

Question 15

A pure copper penny has $$2.81 	imes 10$$^{22}$$ atoms. What is its mass? (Molar mass of Cu = 63.55$$\ \mathrm{g/mol}$$)

Accepted Answer

$$2.97\ \mathrm{g}$$

Question 16

Which of the following is an example of green chemistry?

Accepted Answer

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

Question 17

Which has more atoms: $$10.0\ \mathrm{g} Mg or$$ $$10.0\ \mathrm{g} Ca$$?

Accepted Answer

Magnesium

Question 18

Which of the following has the largest mass?

Accepted Answer

$$10.0\ \mathrm{mol}\ \mathrm{Rb}$$

Question 19

Which reaction is consistent with Dalton’s Atomic Theory?

Accepted Answer

$$\mathrm{C} + \mathrm{H}_2 \rightarrow \mathrm{CH}_4$$

Atoms, Laws of Chemical Combination, and the Periodic Table

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