Question 1

How many moles of NaNO$$_3$$ are present in a 115 g sample? (Molar mass of NaNO$$_3 = 85 g/$$mol)

Accepted Answer

$$1.35$$ mol

Question 2

A sample contains 43.5 g of Mg(NO$$_3$$)$$_2. $$How many moles of Mg(NO$$_3$$)$$_2$$ are present? (Molar mass = 148 g/mol)

Accepted Answer

$$0.294$$ mol

Question 3

How many moles of nitrogen atoms are present in a sample of C$$_2H$_4(NO$_3$$)$$_2$$ that has the same number of O atoms as in 12.4 g of Ca(NO$$_3$$)$$_2$$? (Molar mass of Ca(NO$$_3$$)$$_2 = 164 g/$$mol)

Accepted Answer

$$0.227$$ mol$

Question 4

The hemoglobin content of blood is about 15.5 g per 100 mL. If the molar mass of hemoglobin is $$6.5 	imes 10^4$ g/mol, how many moles of hemoglobin are present in 5.0 L of blood?

Accepted Answer

$$1.19 	imes 10$$^{-2}$$ mol

Question 5

If a person has 5.0 L of blood, and the mass of hemoglobin is 15.5 g per 100 mL, what is the total mass of hemoglobin in the blood?

Accepted Answer

$$775 g$$

Question 6

Benzaldehyde, a compound found in bitter almonds, contains 70.5% C, 5.9% H, and 23.6% O by mass. What is its empirical formula?

Accepted Answer

C$$_7H$_6O$$

Question 7

A compound contains 39.1% C, 4.4% H, and 56.5% O by mass. What is the empirical formula?

Accepted Answer

C$$_2H$_3O$_2$$

Question 8

A sample of a compound contains 0.25 mol of C, 0.50 mol of H, and 0.25 mol of O. What is the empirical formula?

Accepted Answer

CH$$_2O$$

Question 9

The element X forms the compound XCl$$_3$$, containing 65.0% Cl by mass. What is element X?

Accepted Answer

Aluminum

Question 10

Which of the following compounds is ionic?

Accepted Answer

K$$_2CO$_3$$

Question 11

Which of the following compounds contains both ionic and covalent bonds?

Accepted Answer

NaNO$$_3$$

Question 12

Which of the following is a molecular compound?

Accepted Answer

SO$$_2$$

Question 13

Calcium carbide (CaC$$_2) $$reacts with water to produce acetylene gas (C$$_2H$_2) $$and calcium hydroxide. If 5.0 g of CaC$$_2 is $$used, what mass of C$$_2H$_2 is $$produced? (Molar mass CaC$$_2 = 64 g/$$mol, C$$_2H$_2 = 26 g/$$mol)

Accepted Answer

$$2.03 g$$

Question 14

If 12 g of Fe$$_2O$_3 is $$used in a reaction, how many moles of Fe$$_2O$_3$$ are present? (Molar mass = 160 g/mol)

Accepted Answer

$$0.075$$ mol

Question 15

A student mixes 5.0 g of CaC$$_2$$ with excess water. What is the limiting reactant and why?

Accepted Answer

CaC$$_2 is $$the limiting reactant because water is in excess.

Question 16

Which of the following best describes the empirical formula?

Accepted Answer

The simplest whole-number ratio of atoms in a compound.

Question 17

A compound has a molecular formula of C$$_6H$_{12}O$_6. $$What is its empirical formula?

Accepted Answer

CH$$_2O$$

Question 18

Which of the following is NOT a molecular compound?

Accepted Answer

K$$_2SO$_4$$

Question 19

A sample contains 0.50 mol of C, 1.0 mol of H, and 0.50 mol of O. What is the empirical formula?

Accepted Answer

CH$$_2O$$

General Chemistry: Mole Calculations, Empirical Formulas, and Chemical Composition

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