Q: Which of the following best defines Avogadro's number?

The number of particles in 1 mole of a substance, $$6.022 \times 10$$^{23}$$.

Q: A chemist has 0.250 moles of $$\mathrm{CO_2$}. $$How many molecules of $$\mathrm{CO_2$}$$ does this represent?

$$1.51 \times 10$$^{23}$$ molecules

Q: Which of the following statements about the mole is correct?

A mole of any element contains $$6.022 \times 10$$^{23}$$ atoms.

Q: How many oxygen atoms are in 3.00 moles of $$\mathrm{CO_2$}$$?

$$3.61 \times 10$$^{24}$$ atoms

Q: If you have 18.0 g of water ($$\mathrm{H_2O}$$), how many molecules of water do you have? (H = 1.01, O = 16.00)

$$6.02 \times 10$$^{23}$$ molecules

Question 1

Which of the following best defines Avogadro's number?

Accepted Answer

The number of particles in 1 mole of a substance, $$6.022 	imes 10$$^{23}$$.

Question 2

A chemist has 0.250 moles of $$\mathrm{CO_2$}. $$How many molecules of $$\mathrm{CO_2$}$$ does this represent?

Accepted Answer

$$1.51 	imes 10$$^{23}$$ molecules

Question 3

Which of the following statements about the mole is correct?

Accepted Answer

A mole of any element contains $$6.022 	imes 10$$^{23}$$ atoms.

Question 4

How many moles of oxygen atoms are present in 2.00 moles of $$\mathrm{H_2O}$$?

Accepted Answer

4.00 moles

Question 5

What is the molar mass of $$\mathrm{Li_2CO_3} ($$lithium carbonate)? (Atomic masses: Li = 6.94, C = 12.01, O = 16.00)

Accepted Answer

$$73.83\ \mathrm{g/mol}$$

Question 6

A sample contains 58.44 g of NaCl. How many moles of NaCl are present? (Na = 22.99, Cl = 35.45)

Accepted Answer

1.00 mole

Question 7

How many oxygen atoms are in 3.00 moles of $$\mathrm{CO_2$}$$?

Accepted Answer

$$3.61 	imes 10$$^{24}$$ atoms

Question 8

Which of the following is the correct sequence to convert grams of a compound to the number of molecules?

Accepted Answer

Grams $$\rightarrow$$ Moles $$\rightarrow$$ Molecules

Question 9

A balanced chemical equation is: $$2\mathrm{H_2$} + \mathrm{O_2$} \rightarrow 2\mathrm{H_2O}. If $$you start with 4.0 moles of $$\mathrm{H_2$}$$, how many moles of $$\mathrm{H_2O}$$ can be produced?

Accepted Answer

4.0 moles

Question 10

If you have 18.0 g of water ($$\mathrm{H_2O}$$), how many molecules of water do you have? (H = 1.01, O = 16.00)

Accepted Answer

$$6.02 	imes 10$$^{23}$$ molecules

Question 11

Which law states that matter is neither created nor destroyed in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Question 12

A reaction is carried out with 2.0 moles of $$\mathrm{N_2$}$$ and excess $$\mathrm{H_2$}$$ according to $$\mathrm{N_2$} + 3\mathrm{H_2$} \rightarrow 2\mathrm{NH_3$}. $$How many moles of $$\mathrm{NH_3$}$$ are produced?

Accepted Answer

4.0 moles

Question 13

How many moles of sodium atoms are in 3.0 moles of $$\mathrm{Na_2SO_4}$$?

Accepted Answer

6.0 moles

Question 14

A sample of $$\mathrm{$$CaCl_2$$}$$ contains $$1.20 	imes 10$$^{24}$$ formula units. How many moles of $$\mathrm{$$CaCl_2$$}$$ are present?

Accepted Answer

0.199 moles

Question 15

Which of the following is the correct molar mass for $$\mathrm{C_6H_{12}O_6$} ($$glucose)? (C = 12.01, H = 1.01, O = 16.00)

Accepted Answer

$$180.16\ \mathrm{g/mol}$$

Question 16

In a reaction, 10.0 g of $$\mathrm{NH_3$} is $$produced. What is the number of moles of $$\mathrm{NH_3$}$$? (N = 14.01, H = 1.01)

Accepted Answer

0.588 moles

Question 17

A balanced equation is $$2\mathrm{Al} + 3\mathrm{Cl_2$} \rightarrow 2\mathrm{$$AlCl_3$$}. If $$you start with 5.0 moles of $$\mathrm{Cl_2$}$$, how many moles of $$\mathrm{$$AlCl_3$$}$$ can be formed?

Accepted Answer

3.33 moles

Question 18

Which of the following is NOT a correct use of Avogadro's number?

Accepted Answer

To convert grams directly to number of atoms.

Question 19

A sample of $$\mathrm{Na_2SO_4}$$ weighs 142 g. How many moles are present? (Na = 22.99, S = 32.07, O = 16.00)

Accepted Answer

1.00 mole

Question 20

In a real-world scenario, a hospital needs to prepare 0.50 moles of $$\mathrm{KCl}$$ solution for a patient. What mass of $$\mathrm{KCl} is $$required? (K = 39.10, Cl = 35.45)

Accepted Answer

37.28 g

Moles, Molar Mass, and Chemical Equations: Study Notes for General Chemistry

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