Q: Which of the following is equivalent to Avogadro's number?

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

Q: A sample contains $$0.250$$ moles of $$CO_2. $$How many $$CO_2$$ molecules are present in the sample?

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

Q: How many atoms of oxygen are in $$0.200$$ moles of aspirin ($$C_9H_8O_4$$)?

$$4.82 \times 10$$^{23}$$ atoms

Question 1

Which of the following is equivalent to Avogadro's number?

Accepted Answer

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

Question 2

A sample contains $$0.250$$ moles of $$CO_2. $$How many $$CO_2$$ molecules are present in the sample?

Accepted Answer

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

Question 3

How many atoms of oxygen are in $$0.200$$ moles of aspirin ($$C_9H_8O_4$$)?

Accepted Answer

$$4.82 	imes 10$$^{23}$$ atoms

Question 4

What is the molar mass of $$C_2H_6O ($$ethanol)?

Accepted Answer

$$46.08 g/$$mol

Question 5

A box of table salt ($$NaCl) $$contains $$737 g of$$ $$NaCl. $$How many moles of $$NaCl$$ are in the box? (Molar mass of $$NaCl = 58.44 g/$$mol)

Accepted Answer

$$12.6$$ moles

Question 6

Which of the following best describes the law of conservation of mass?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 7

In the reaction $$2Fe(s) + 3S(s) \rightarrow Fe_2S_3(s)$$, what is the mole ratio of $$Fe to$$ $$S$$?

Accepted Answer

$$2:3$$

Question 8

How many moles of $$Fe_2O_3$$ can be formed from $$9.0$$ moles of $$O_2 in $$the reaction $$4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$$?

Accepted Answer

$$6.0$$ moles

Question 9

A sample of water has a mass of $$59.8$$ grams. How many moles of water are in the sample? (Molar mass of $$H_2O = 18.02 g/$$mol)

Accepted Answer

$$3.32$$ moles

Question 10

If $$3.00$$ moles of $$CO$$ and $$5.00$$ moles of $$H_2$$ react to form methanol ($$CH_4O) $$according to $$CO(g) + 2H_2(g) \rightarrow CH_4O(g)$$, what is the limiting reactant and how many moles of $$CH_4O$$ can be produced?

Accepted Answer

$$H_2 is $$limiting; $$2.50$$ moles of $$CH_4O$$ can be produced.

Question 11

How many grams of $$O_2$$ are needed to produce $$45.8$$ grams of $$Fe_2O_3 in $$the reaction $$4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$$? (Molar mass: $$Fe_2O_3 = 159.7 g/$$mol, $$O_2 = 32.00$ g/mol)

Accepted Answer

$$13.8 g$$

Question 12

A ceramic brake disc in a sports car is made from silicon carbide ($$SiC). If$$ $$70.0$$ grams of $$SiO_2$$ and $$50.0$$ grams of $$C$$ react according to $$SiO_2(s) + 3C(s$$) \rightarrow SiC(s) + 2CO(g)$$, which reactant is limiting?

Accepted Answer

$$SiO_2 is $$the limiting reactant.

Question 13

What is the percent yield if $$50.0$$ grams of $$LiOH$$ produces $$72.8$$ grams of $$LiHCO_3 in $$the reaction $$LiOH(s) + CO_2$(g) \rightarrow $$LiHCO_3$$(s)$$? (Molar mass: $$LiOH = 23.95 g/$$mol, $$LiHCO_3 = 67.96$ g/mol)

Accepted Answer

$$85.0\%$$

Question 14

Which of the following is NOT a correct conversion factor for $$1$$ mole of $$C_9H_8O_4 ($$aspirin)?

Accepted Answer

$$1$$ mole $$C_9H_8O_4 = 12$$ moles $$C$$

Question 15

Which of the following best describes a limiting reactant in a chemical reaction?

Accepted Answer

It is the reactant that is completely consumed first, limiting the amount of product formed.

Question 16

If you have $$1.8 	imes 10$$^{24}$$ atoms of sulfur, how many moles of sulfur do you have?

Accepted Answer

$$3.0$$ moles

Question 17

Which of the following is the correct molar mass for lithium carbonate ($$Li_2CO_3$$)? (Atomic masses: $$Li = 6.94 g/$$mol, $$C = 12.01 g/$$mol, $$O = 16.00 g/$$mol)

Accepted Answer

$$73.89 g/$$mol

The Mole, Molar Mass, and Chemical Calculations in GOB Chemistry

Guida di studio - Domande di pratica

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