Q: How many molecules are present in $$0.25$$ moles of $$CO_2$$? ($$Avogadro's\ number = 6.022 \times 10$$^{23}$$)

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

Q: Which formula is used to calculate the concentration of a solution in molarity ($$M$$)?

$$M = \dfrac{\text{moles of solute}}{\text{volume of solution (L)}}$$

Q: Which formula is used to calculate percent yield in a chemical reaction?

$$\text{Percent Yield} = \dfrac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%$$

Question 1

Which of the following best describes the difference between molecular mass and molar mass?

Accepted Answer

Molecular mass is the sum of the atomic masses of all atoms in a molecule (in amu), while molar mass is the mass of one mole of that substance (in g/mol).

Question 2

A sample contains $$18.0$$ grams of water ($$H_2O). $$How many moles of water are present in the sample? ($$Molar\ mass\ of\ H_2O = 18.0\ g/mol)$$

Accepted Answer

$$1.0$$ mole

Question 3

How many molecules are present in $$0.25$$ moles of $$CO_2$$? ($$Avogadro's\ number = 6.022 	imes 10$$^{23}$$)

Accepted Answer

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

Question 4

Which formula is used to calculate the concentration of a solution in molarity ($$M$$)?

Accepted Answer

$$M = \dfrac{	ext{moles of solute}}{	ext{volume of solution (L)}}$$

Question 5

A $$0.50 L $$solution contains $$0.10$$ moles of $$NaCl. $$What is the molarity of the solution?

Accepted Answer

$$0.20\ M$$

Question 6

Which of the following best illustrates the Law of Conservation of Mass in a chemical reaction?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 7

Which of the following is a balanced chemical equation for the synthesis of water from hydrogen and oxygen?

Accepted Answer

$$2H_2 + O_2$ \rightarrow 2H_2O$$

Question 8

Which type of chemical reaction is represented by the following equation? $$2KClO_3 \rightarrow 2KCl + 3O_2$$

Accepted Answer

Decomposition

Question 9

Which of the following reactions is a precipitation reaction?

Accepted Answer

$$AgNO_3(aq) + $$NaCl(aq) \rightarrow AgCl(s) + $$NaNO_3(aq$$)$$

Question 10

Given the reaction $$2Na + Cl_2$ \rightarrow 2NaCl$$, which element is oxidized and which is reduced?

Accepted Answer

Na is oxidized, Cl is reduced.

Question 11

What is the oxidation number of sulfur in $$SO_2$$?

Accepted Answer

$$+4$$

Question 12

If $$3.0$$ moles of $$Fe$$ react with $$4.5$$ moles of $$O_2 to $$produce $$Fe_2O_3$$ according to the equation $$4Fe + 3O_2 \rightarrow 2Fe_2O_3$$, how many moles of $$Fe_2O_3$$ are produced?

Accepted Answer

$$1.5$$ moles

Question 13

Which of the following best describes a double displacement reaction?

Accepted Answer

Two compounds exchange ions to form two new compounds.

Question 14

A student mixes $$BaCl_2(aq$$)$$ and Na_2SO_4(aq$$)$$. According to the solubility chart, $$BaSO_4$$ is insoluble. What will happen?

Accepted Answer

$$BaSO_4$$ will precipitate out of solution.

Question 15

Which formula is used to calculate percent yield in a chemical reaction?

Accepted Answer

$$	ext{Percent Yield} = \dfrac{	ext{Actual Yield}}{	ext{Theoretical Yield}} 	imes 100\%$$

Question 16

A reaction has a theoretical yield of $$10.0$$ grams, but only $$7.5$$ grams are actually produced. What is the percent yield?

Accepted Answer

$$75\%$$

Question 17

Which of the following is an example of an acid-base neutralization reaction?

Accepted Answer

$$HCl(aq) + NaOH(aq) \rightarrow NaCl(aq) + H_2O(l)$$

Question 18

How many grams of $$Na_2SO_4$$ are needed to prepare $$0.25$$ moles? ($$Molar\ mass\ of\ Na_2SO_4 = 142\ g/mol)$$

Accepted Answer

$$35.5$$ grams

Question 19

Which of the following best describes a redox reaction?

Accepted Answer

A reaction in which electrons are transferred between species.

General Chemistry Study Guide: Mole Calculations, Chemical Reactions, and Solution Chemistry

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