Q: According to Table 3.2, how many chloride ions are present in 1 mole of BaCl$$_2$$?

$$2 \times 6.02 \times 10$$^{23}$$

Q: Which of the following is the correct calculation for percent composition by mass of carbon in C$$_{12}H$_{22}O$_{11} ($$sucrose)?

$$\frac{12 \times 12.01}{342.3} \times 100$$

Question 1

Which of the following best describes the law demonstrated by the balanced equation $$2 \mathrm{H}_2 + \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} as $$shown in the first image?

Accepted Answer

The law of conservation of mass

Question 2

In the reaction $$2 \mathrm{H}_2 + \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O}$$, how many molecules of water are produced from 3 molecules of $$\mathrm{O}_2 if $$hydrogen is in excess?

Accepted Answer

6 molecules

Question 3

Which of the following statements is TRUE regarding coefficients and subscripts in chemical equations?

Accepted Answer

Coefficients change the amount of substance, while subscripts change the identity of the substance.

Question 4

Given the pie chart in the second image, which best represents a compound with a percent composition of approximately 42% carbon, 6% hydrogen, and 52% oxygen by mass?

Accepted Answer

C$$_{12}H$_{22}O$_{11} ($$sucrose)

Question 5

According to Table 3.2, how many chloride ions are present in 1 mole of BaCl$$_2$$?

Accepted Answer

$$2 	imes 6.02 	imes 10$$^{23}$$

Question 6

A student has 0.346 mol of ethylene ($$\mathrm{C}_2\mathrm{H}_4). $$How many molecules does this represent?

Accepted Answer

$$2.08 	imes 10$$^{23}$$

Question 7

Which of the following is the correct molar mass for glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$)?

Accepted Answer

$$180.12\ \mathrm{g/mol}$$

Question 8

If 7.834 g of glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6) is $$present, how many moles does this represent? (Molar mass = $$180.12\ \mathrm{g/mol})$$

Accepted Answer

$$0.0435$$ mol

Question 9

A reaction requires 5.00 mmol NaCl. How many grams of NaCl should be massed? (Molar mass = $$58.44\ \mathrm{g/mol})$$

Accepted Answer

$$0.292 g$$

Question 10

A 5.325-g sample of methyl benzoate contains 3.758 g of carbon, 0.316 g of hydrogen, and 1.251 g of oxygen. What is the empirical formula?

Accepted Answer

$$\mathrm{C}_4\mathrm{H}_4\mathrm{O}$$

Question 11

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

Accepted Answer

The reactant that is completely consumed and determines the amount of product formed.

Question 12

If 2.00 g of Zn and 2.50 g of AgNO$$_3$$ are combined and the theoretical yield of Zn(NO$$_3$$)$$_2 is 1.39 g$$, but only 1.12 g is recovered, what is the percent yield?

Accepted Answer

$$80.6\%$$

Question 13

Which of the following is a correct mole ratio for the reaction $$2 \mathrm{H}_2 + \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O}$$?

Accepted Answer

$$2\ \mathrm{mol}\ \mathrm{H}_2 : 1\ \mathrm{mol}\ \mathrm{O}_2$$

Question 14

A compound has an empirical formula of HCO$$_2$$ and a molar mass of 90.0 g/mol. What is its molecular formula?

Accepted Answer

$$\mathrm{H}_2\mathrm{C}_2\mathrm{O}_4$$

Question 15

How many grams of CO$$_2$$ are produced when 3.81 g of C$$_4H$_{10} is $$burned in excess oxygen? (Molar mass C$$_4H$_{10} = 58.14 g/$$mol, CO$$_2 = 44.01 g/$$mol, $$2 \mathrm{C}_4\mathrm{H}_{10} + 13 \mathrm{O}_2 \rightarrow 8 \mathrm{CO}_2 + 10 \mathrm{H}_2\mathrm{O})$$

Accepted Answer

$$11.5 g$$

Question 16

Which of the following is the correct calculation for percent composition by mass of carbon in C$$_{12}H$_{22}O$_{11} ($$sucrose)?

Accepted Answer

$$\frac{12 	imes 12.01}{342.3} 	imes 100$$

Question 17

A reaction produces 6900 ng of CO$$_2. $$How many kmol of CO$$_2 is $$this? (Molar mass CO$$_2 = 44.01 g/$$mol)

Accepted Answer

$$1.6 	imes 10$$^{-10}$$ kmol

Question 18

Which of the following best describes a combination reaction?

Accepted Answer

Two or more reactants combine to form a single product.

Stoichiometry and Chemical Equations: Calculations with Chemical Formulas

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