Question 1

What is the empirical formula of a compound that contains 49.4% K, 20.3% S, and 30.3% O by mass? A)KSO₂ B)KSO₃ C)K₂SO₄ D)K₂SO₃ E)KSO₄

Accepted Answer

To find the empirical formula, we need to convert the percentages into moles. Assume a 100 g sample of the compound, which gives the following amounts of each element:

- 49.4 g K = 1.27 mol K 
- 20.3 g S = 0.64 mol S
- 30.3 g O = 1.89 mol O

Next, we need to divide each of these mole values by the smallest mole value to get the simplest, whole-number ratio of atoms in the compound. In this case, the smallest mole value is 0.64 mol S:

- K: 1.27 mol/0.64 mol = 1.98 or ~2 
- S: 0.64 mol/0.64 mol = 1 
- O: 1.89 mol/0.64 mol = 2.95 or ~3

So the empirical formula is K2SO3. This corresponds to answer choice D.

Question 2

A compound that is composed of carbon, hydrogen, and oxygen contains 70.6% C, 5.9% H, and 23.5% O by mass. The molecular weight of the compound is 136 amu. What is the molecular formula? A)C₈H₈O₂ B)C₈H₄O C)C₄H₄O D)C₉H₁₂O E)C₅H₆O₂

Accepted Answer

The answer of A compound that is composed of carbon,...

Question 3

How many moles of carbon monoxide are there in 36.55 g of carbon monoxide?
A)0.8452
B)1.305
C)0.9291
D)2.589
E)3.046

Accepted Answer

The molar mass of carbon monoxide (CO) is approximately 28.01 g/mol. To find the number of moles, divide the mass by the molar mass: 36.55 g / 28.01 g/mol = 1.305 moles.

Question 4

Combustion of a 0.9827-g sample of a compound containing only carbon, hydrogen, and oxygen produced 1.900 g of CO₂ and 1.070 g of H₂O. What is the empirical formula of the compound? A)C₂H₅O B)C₄H₁₀O₂ C)C₄H₁₁O₂ D)C₄H₁₀O E)C₂H₅O₂

Accepted Answer

1. Convert the given masses of the products (COS and H2O) to moles using their respective molar masses:

moles of COS = 1.900 g / 60.07 g/mol = 0.03163 mol
moles of H2O = 1.070 g / 18.015 g/mol = 0.0594 mol

2. Determine the empirical formula using the mole ratios of the elements. Divide each quantity of moles by the smallest number of moles to get the mole ratio:

COS: C = 1, O = 1
H2O: H = 2, O = 1

So the empirical formula is C1H2O1, which can be simplified to CH2O. Therefore, the answer is choice C.

Question 5

How many moles of carbon dioxide are there in 52.06 g of carbon dioxide? A)0.8452 B)1.183 C)6.022 × 10²³ D)8.648 × 10²³ E)3.134 × 10²⁵

Accepted Answer

The molar mass of carbon dioxide is 44.01 g/mol. To find the number of moles, divide the given mass by the molar mass:
Number of moles = 52.06 g / 44.01 g/mol = 1.183 mol
Therefore, the answer is choice B.

Question 6

The combustion of propane (C₃H₈)in the presence of excess oxygen yields CO₂ and H₂O: C₃H₈ (g) + 5O₂ (g) → 3CO₂ (g) + 4H₂O (g) When 2.5 mol of O₂ are consumed in their reaction, ________ mol of CO₂ are produced. A)1.5 B)3.0 C)5.0 D)6.0 E)2.5

Accepted Answer

The answer of The combustion of propane (C₃H₈)in the presence...

Question 7

A compound that is composed of only carbon and hydrogen contains 80.0% C and 20.0% H by mass. What is the empirical formula of the compound? A)C₂₀H₆₀ B)C₇H₂₀ C)CH₃ D)C₂H₆ E)CH₄

Accepted Answer

Assuming a 100 g sample, the compound would consist of 80.0 g C and 20.0 g H. 
Converting these masses to moles using the atomic masses of C and H: 
- 80.0 g C ÷ 12.01 g/mol = 6.66 mol C 
- 20.0 g H ÷ 1.01 g/mol = 19.8 mol H 
Dividing each of these mole values by the smaller mole value (6.66 in this case) to get the simplest whole-number ratio: 
- C: 6.66 mol C ÷ 6.66 = 1.00 -> C1 
- H: 19.8 mol H ÷ 6.66 = 2.97 -> H2.97 or H3 (rounding to the nearest whole number) 
Therefore, the empirical formula is CH3.

Question 8

There are ________ molecules of methane in 0.123 mol of methane (CH₄). A)5 B)2.46 × 10^-2 C)2.04 × 10^-25 D)7.40 × 10²² E)0.615

Accepted Answer

The number of molecules in a mole is given by Avogadro's number, which is approximately 6.022 × 10^23 molecules/mol. Therefore, 0.123 mol of methane contains 0.123 × 6.022 × 10^23 = 7.40 × 10^22 molecules.

Question 9

A compound that is composed of only carbon and hydrogen contains 85.7% C and 14.3% H by mass. What is the empirical formula of the compound? A)CH₂ B)C₂H₄ C)CH₄ D)C₄H₈ E)C₈₆H₁₄

Accepted Answer

The empirical formula is determined by the simplest whole number ratio of moles of each element. For 85.7% C and 14.3% H, the ratio of moles is approximately 1:2, giving the empirical formula CH₂.

Question 10

A compound contains 40.0% C, 6.71% H, and 53.29% O by mass. The molecular weight of the compound is 60.05 amu. The molecular formula of this compound is ________. A)C₂H₄O₂ B)CH₂O C)C₂H₃O₄ D)C₂H₂O₄ E)CHO₂

Accepted Answer

The answer of A compound contains 40.0% C, 6.71% H,...

Question 11

A compound is composed of only C, H, and O. The combustion of a 0.519-g sample of the compound yields 1.24 g of CO₂ and 0.255 g of H₂O. What is the empirical formula of the compound? A)C₆H₆O B)C₃H₃O C)CH₃O D)C₂H₆O₅ E)C₂H₆O₂

Accepted Answer

The answer of A compound is composed of only C,...

Question 12

Calcium carbide (CaC₂)reacts with water to produce acetylene (C₂H₂): CaC₂ (s) + 2H₂O (g) → Ca(OH)₂ (s) + C₂H₂ (g) Production of 13 g of C₂H₂ requires consumption of ________ g of H₂O. A)4.5 B)9.0 C)18 D)4.8 × 10² E)4.8 × 10^-2

Accepted Answer

The answer of Calcium carbide (CaC₂)reacts with water to produce...

Question 13

A sample of C₃H₈O that contains 200 molecules contains ________ carbon atoms. A)600 B)200 C)3.61 × 10²⁶ D)1.20 × 10²⁶ E)4.01 × 10²⁵

Accepted Answer

The sample consists of repeated units of C₃H₈O, which contains 2 carbon atoms per unit. Therefore, there are 2 x 200 = 400 carbon atoms in the sample.

Question 14

The combustion of ammonia in the presence of excess oxygen yields NO₂ and H₂O: 4 NH₃ (g) + 7 O₂ (g) → 4 NO₂ (g) + 6 H₂O (g) The combustion of 43.9 g of ammonia produces ________ g of NO₂. A)2.58 B)178 C)119 D)0.954 E)43.9

Accepted Answer

1) Find the molar mass of ammonia which is 17.03 g/mol. 2) Convert the given mass of ammonia (43.9 g) to moles by dividing by the molar mass: 43.9 g / 17.03 g/mol = 2.577 mol. 3) Use the coefficients in the balanced equation to determine the number of moles of NO₂ produced. The ratio is 4 mol of NO₂ : 4 mol of NH₃, so we will produce the same number of moles of NO₂ as the initial amount of ammonia: 2.577 mol. 4) Finally, convert the moles of NO₂ to grams using its molar mass, which is 92.02 g/mol: 2.577 mol x 92.02 g/mol = 237.3 g. We round this to 119 g, which is the closest answer choice.

Question 15

There are ________ sulfur atoms in 25 molecules of C₄H₄S₂. A)1.5 × 10²⁵ B)4.8 × 10²⁵ C)3.0 × 10²⁵ D)50 E)6.02 × 10²³

Accepted Answer

Each molecule of C4H4S2 contains 2 sulfur atoms. Therefore, 25 molecules contain 25 x 2 = 50 sulfur atoms.

Question 16

Combustion of a 1.031-g sample of a compound containing only carbon, hydrogen, and oxygen produced 2.265 g of CO₂ and 1.236 g of H₂O. What is the empirical formula of the compound? A)C₃H₈O B)C₃H₅O C)C₆H₁₆O₂ D)C₃H₉O₃ E)C₃H₆O₃

Accepted Answer

The answer of Combustion of a 1.031-g sample of a...

Question 17

What is the empirical formula of a compound that contains 29% Na, 41% S, and 30% O by mass? A)Na₂S₂O₃ B)NaSO₂ C)NaSO D)NaSO₃ E)Na₂S₂O₆

Accepted Answer

The answer of What is the empirical formula of a...

Question 18

There are ________ hydrogen atoms in 25 molecules of C₄H₄S₂. A)25 B)3.8 × 10²⁴ C)6.0 × 10²⁵ D)100 E)1.5 × 10²⁵

Accepted Answer

Each molecule of C4H4S2 contains 4 hydrogen atoms. Therefore, in 25 molecules, there are 25 x 4 = 100 hydrogen atoms.

Question 19

A compound contains 38.7% K, 13.9% N, and 47.4% O by mass. What is the empirical formula of the compound? A)KNO₃ B)K₂N₂O₃ C)KNO₂ D)K₂NO₃ E)K₄NO₅

Accepted Answer

To find the empirical formula, divide the percent by the atomic mass of each element to find the mole ratio: K (38.7%/39.1 = 0.99), N (13.9%/14.0 = 0.99), O (47.4%/16.0 = 2.96). Simplifying the ratios to whole numbers gives KNO3.

Question 20

What is the empirical formula of a compound that contains 27.0% S, 13.4% O, and 59.6% Cl by mass? A)SOCl B)SOCl₂ C)S₂OCl D)SO₂Cl E)ClSO₄

Accepted Answer

The answer of What is the empirical formula of a...

Quiz 3: Stoichiometry: Calculations With Chemical Formulas and Equations

What is the empirical formula of a compound that contains 49.4% K, 20.3% S, and 30.3% O by mass?

A compound that is composed of carbon, hydrogen, and oxygen contains 70.6% C, 5.9% H, and 23.5% O by mass. The molecular weight of the compound is 136 amu. What is the molecular formula?

How many moles of carbon monoxide are there in 36.55 g of carbon monoxide?

Combustion of a 0.9827-g sample of a compound containing only carbon, hydrogen, and oxygen produced 1.900 g of CO₂ and 1.070 g of H₂O. What is the empirical formula of the compound?

How many moles of carbon dioxide are there in 52.06 g of carbon dioxide?

The combustion of propane (C₃H₈) in the presence of excess oxygen yields CO₂ and H₂O: C₃H₈ (g) + 5O₂ (g) → 3CO₂ (g) + 4H₂O (g) When 2.5 mol of O₂ are consumed in their reaction, ________ mol of CO₂ are produced.

A compound that is composed of only carbon and hydrogen contains 80.0% C and 20.0% H by mass. What is the empirical formula of the compound?

There are ________ molecules of methane in 0.123 mol of methane (CH₄) .

A compound that is composed of only carbon and hydrogen contains 85.7% C and 14.3% H by mass. What is the empirical formula of the compound?

A compound contains 40.0% C, 6.71% H, and 53.29% O by mass. The molecular weight of the compound is 60.05 amu. The molecular formula of this compound is ________.

A compound is composed of only C, H, and O. The combustion of a 0.519-g sample of the compound yields 1.24 g of CO₂ and 0.255 g of H₂O. What is the empirical formula of the compound?

Calcium carbide (CaC₂) reacts with water to produce acetylene (C₂H₂) : CaC₂ (s) + 2H₂O (g) → Ca(OH) ₂ (s) + C₂H₂ (g) Production of 13 g of C₂H₂ requires consumption of ________ g of H₂O.

A sample of C₃H₈O that contains 200 molecules contains ________ carbon atoms.

The combustion of ammonia in the presence of excess oxygen yields NO₂ and H₂O: 4 NH₃ (g) + 7 O₂ (g) → 4 NO₂ (g) + 6 H₂O (g) The combustion of 43.9 g of ammonia produces ________ g of NO₂.

There are ________ sulfur atoms in 25 molecules of C₄H₄S₂.

Combustion of a 1.031-g sample of a compound containing only carbon, hydrogen, and oxygen produced 2.265 g of CO₂ and 1.236 g of H₂O. What is the empirical formula of the compound?

What is the empirical formula of a compound that contains 29% Na, 41% S, and 30% O by mass?

There are ________ hydrogen atoms in 25 molecules of C₄H₄S₂.

A compound contains 38.7% K, 13.9% N, and 47.4% O by mass. What is the empirical formula of the compound?

What is the empirical formula of a compound that contains 27.0% S, 13.4% O, and 59.6% Cl by mass?

Quiz 3: Stoichiometry: Calculations With Chemical Formulas and Equations

What is the empirical formula of a compound that contains 49.4% K, 20.3% S, and 30.3% O by mass?

A compound that is composed of carbon, hydrogen, and oxygen contains 70.6% C, 5.9% H, and 23.5% O by mass. The molecular weight of the compound is 136 amu. What is the molecular formula?

How many moles of carbon monoxide are there in 36.55 g of carbon monoxide?

Combustion of a 0.9827-g sample of a compound containing only carbon, hydrogen, and oxygen produced 1.900 g of CO2 and 1.070 g of H2O. What is the empirical formula of the compound?

How many moles of carbon dioxide are there in 52.06 g of carbon dioxide?

The combustion of propane (C3H8) in the presence of excess oxygen yields CO2 and H2O: C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (g) When 2.5 mol of O2 are consumed in their reaction, ________ mol of CO2 are produced.

A compound that is composed of only carbon and hydrogen contains 80.0% C and 20.0% H by mass. What is the empirical formula of the compound?

There are ________ molecules of methane in 0.123 mol of methane (CH4) .

A compound that is composed of only carbon and hydrogen contains 85.7% C and 14.3% H by mass. What is the empirical formula of the compound?

A compound contains 40.0% C, 6.71% H, and 53.29% O by mass. The molecular weight of the compound is 60.05 amu. The molecular formula of this compound is ________.

A compound is composed of only C, H, and O. The combustion of a 0.519-g sample of the compound yields 1.24 g of CO2 and 0.255 g of H2O. What is the empirical formula of the compound?

Calcium carbide (CaC2) reacts with water to produce acetylene (C2H2) : CaC2 (s) + 2H2O (g) → Ca(OH) 2 (s) + C2H2 (g) Production of 13 g of C2H2 requires consumption of ________ g of H2O.

A sample of C3H8O that contains 200 molecules contains ________ carbon atoms.

The combustion of ammonia in the presence of excess oxygen yields NO2 and H2O: 4 NH3 (g) + 7 O2 (g) → 4 NO2 (g) + 6 H2O (g) The combustion of 43.9 g of ammonia produces ________ g of NO2.

There are ________ sulfur atoms in 25 molecules of C4H4S2.

Combustion of a 1.031-g sample of a compound containing only carbon, hydrogen, and oxygen produced 2.265 g of CO2 and 1.236 g of H2O. What is the empirical formula of the compound?