Question 1

If a 1.59 gram sample of a carbon-containing compound is burned in air, 1.01 gram of CO₂ is produced. What is the percent carbon in the compound?

Accepted Answer

To find the percent carbon, first calculate the mass of carbon in the CO2 produced. The molar mass of CO2 is 44.01 g/mol, and the molar mass of carbon is 12.01 g/mol. The mass of carbon in 1.01 g of CO2 is (12.01/44.01) * 1.01 g = 0.275 g. The percent carbon in the compound is (0.275 g / 1.59 g) * 100% = 17.3%, which rounds to 17%.

Question 2

Analysis of an unknown nickel oxide compound indicated that the molar ratio of nickel to oxygen was 0.167 to 0.251, respectively. What is the empirical formula for the compound?

Accepted Answer

To find the empirical formula, divide the given molar ratios by the smallest ratio: 0.167/0.167 = 1 for Ni and 0.251/0.167 ≈ 1.5 for O. Multiplying both by 2 to get whole numbers gives Ni₂O₃.

Question 3

A sample of an ionic compound was analyzed and found to contain 6.072 g of sodium, 8.474 g of sulfur, and 6.336 g of oxygen. What is its empirical formula?

Accepted Answer

The molar masses are approximately: Na = 23 g/mol, S = 32 g/mol, O = 16 g/mol. Moles of each element: Na = 6.072/23 ≈ 0.264, S = 8.474/32 ≈ 0.265, O = 6.336/16 ≈ 0.396. The simplest ratio is approximately 2:2:3, giving Na2S2O3.

Question 4

Analysis of an unknown sample indicated the sample contained 0.140 grams of N and 0.320 grams of O. The molar mass of the compound was determined to be 92.02 amu. What is the molecular formula of the compound?

Accepted Answer

The empirical formula is NO2, with a molar mass of 46.01 amu. The molecular formula is a multiple of the empirical formula. Since 92.02 amu is approximately twice 46.01 amu, the molecular formula is N2O4.

Question 5

Carbohydrates have an empirical formula of CH₂O. What is the molecular formula of the sugar maltose if it has a molar mass of 180.18?

Accepted Answer

The molecular formula of maltose, which is a disaccharide made from two glucose units, is C12H22O11. However, the question seems to have a typo regarding the molar mass of maltose, which is actually around 342 g/mol, not 180.18 g/mol. The correct molecular formula for a carbohydrate with a molar mass close to 180 would be for glucose (C6H12O6), not maltose. Despite this, based on the options provided and assuming a doubling of the glucose unit for maltose, option D (C12H22O11) is the closest to the expected molecular formula for maltose.

Question 6

Octane is a principle component of gasoline. The empirical formula of octane is C₄H₉, and the molar mass of octane is 114.26 grams per mole. What is the molecular formula of octane?

Accepted Answer

The empirical formula mass of C4H9 is 57.13 g/mol. The molecular formula is a multiple of the empirical formula. 114.26 g/mol divided by 57.13 g/mol is approximately 2, so the molecular formula is C8H18.

Question 7

The empirical formula of a compound was determined to be P₂O₃. The molecular weight of the compound is 220 g/mol. What is the molecular formula of the compound?

Accepted Answer

The empirical formula P₂O₃ has a molar mass of approximately 110 g/mol. The molecular weight of the compound is 220 g/mol, which is twice the empirical formula mass, indicating the molecular formula is P₄O₆.

Question 8

Determine the percentage composition for the compound C₁₀H₁₄N₂.

Accepted Answer

The answer of Determine the percentage composition for the compound...

Question 9

Match the statements on the left with an appropriate response from the right. Responses on the right may be used more than once or need not be used at all.
-________ has a mass of 4.0 grams

Accepted Answer

1/4 mole of CH4 has a mass of 4.0 grams because the molar mass of CH4 is 16 g/mol, so 1/4 mole of CH4 would have a mass of 4 g.

Question 10

Match the statements on the left with an appropriate response from the right. Responses on the right may be used more than once or need not be used at all. -________ contains 1.20 x 10²⁴ molecules

Accepted Answer

One mole of any substance contains Avogadro's number of molecules, which is approximately 6.022 x 10^23. Therefore, 2 moles of H2O would contain 2 x 6.022 x 10^23 = 1.2044 x 10^24 molecules, which is approximately 1.20 x 10^24 molecules.

Question 11

Match the statements on the left with an appropriate response from the right. Responses on the right may be used more than once or need not be used at all.
-________ contains 1 mole of atoms

Accepted Answer

1/4 mole of NH₃ contains 1 mole of atoms because NH₃ has 4 atoms per molecule (1 N and 3 H), so 1/4 mole of NH₃ contains 1 mole of atoms (4 atoms/molecule * 1/4 mole = 1 mole of atoms).

Question 12

Match the statements on the left with an appropriate response from the right. Responses on the right may be used more than once or need not be used at all.
-________ contains 4 moles of H atoms

Accepted Answer

The answer of Match the statements on the left with...

Question 13

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) formula mass of CBr₄(II) formula mass of P₂S₃

Accepted Answer

The formula mass of CBr₄ is greater than that of P₂S₃ because bromine has a higher atomic mass than phosphorus and sulfur, and CBr₄ contains four bromine atoms.

Question 14

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) grams in 1 mole of SiF₄(II) grams in 1 mole of AsF₃

Accepted Answer

The molar mass of SiF4 is less than that of AsF3. Silicon (Si) has a lower atomic mass than arsenic (As), and both compounds have fluorine (F) atoms, so the overall molar mass of SiF4 is less than that of AsF3.

Question 15

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) moles in 50 grams of N₂(II) moles in 50 grams of H₂S

Accepted Answer

To compare the moles in 50 grams of each substance, we need to calculate the molar mass of each and then divide 50 grams by the respective molar masses. N₂ (N₂B₁₂H₁₀) has a lower molar mass compared to H₂S (H₂B₁₂H₁₀S), meaning for the same mass (50 grams), the substance with the lower molar mass (N₂B₁₂H₁₀) will have more moles.

Question 16

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) molecules in 3 moles of SO₂(II) molecules in 3 moles of SO₃

Accepted Answer

The number of molecules in 3 moles of any substance is always the same, regardless of the substance, because a mole is defined as a specific number of entities (Avogadro's number, 6.022 x 10^23). Therefore, 3 moles of SOS1U1B12S1 and 3 moles of SOS1U1B13S1 contain the same number of molecules.

Question 17

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) atoms in 2 moles of NO₂(II) atoms in 2 moles of N₂O

Accepted Answer

Both molecules have the same number of atoms per molecule (1 nitrogen, 12 boron, 1 oxygen), so 2 moles of each will contain the same total number of atoms.

Question 18

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) molecules in 28 grams of Cl₂(II) molecules in 28 grams of NaCl

Accepted Answer

The answer of Contrast the two members of each pair...

Question 19

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) moles of N atoms in 34 g NH₃(II) moles of N atoms in 28 g of N₂

Accepted Answer

Both scenarios involve calculating the moles of nitrogen atoms in different compounds, but the mass given does not directly affect the comparison since the question is about the moles of nitrogen atoms specifically, not the total moles of compound. Assuming both compounds contain nitrogen in the same proportion by mass, the number of moles of nitrogen atoms would be determined by the molar mass of nitrogen and the proportion of nitrogen in each compound, not directly by the total mass of each sample.

Question 20

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) moles of O atoms in Avogadro's number of SO₂ molecules(II) moles of O atoms in twice Avogadro's number of CO molecule

Accepted Answer

Both scenarios describe the same number of oxygen atoms, as Avogadro's number of SO₂ molecules contains Avogadro's number of oxygen atoms, and twice Avogadro's number of CO molecules also contains Avogadro's number of oxygen atoms.

Quiz 9: Chemical Calculations: the Mole Concept and Chemical Formulas

If a 1.59 gram sample of a carbon-containing compound is burned in air, 1.01 gram of CO2 is produced. What is the percent carbon in the compound?

Analysis of an unknown nickel oxide compound indicated that the molar ratio of nickel to oxygen was 0.167 to 0.251, respectively. What is the empirical formula for the compound?

A sample of an ionic compound was analyzed and found to contain 6.072 g of sodium, 8.474 g of sulfur, and 6.336 g of oxygen. What is its empirical formula?

Analysis of an unknown sample indicated the sample contained 0.140 grams of N and 0.320 grams of O. The molar mass of the compound was determined to be 92.02 amu. What is the molecular formula of the compound?

Carbohydrates have an empirical formula of CH2O. What is the molecular formula of the sugar maltose if it has a molar mass of 180.18?

Octane is a principle component of gasoline. The empirical formula of octane is C4H9, and the molar mass of octane is 114.26 grams per mole. What is the molecular formula of octane?

The empirical formula of a compound was determined to be P2O3. The molecular weight of the compound is 220 g/mol. What is the molecular formula of the compound?

Determine the percentage composition for the compound C10H14N2.

Match the statements on the left with an appropriate response from the right. Responses on the right may be used more than once or need not be used at all. -________ has a mass of 4.0 grams

Match the statements on the left with an appropriate response from the right. Responses on the right may be used more than once or need not be used at all. -________ contains 1.20 x 1024 molecules

Match the statements on the left with an appropriate response from the right. Responses on the right may be used more than once or need not be used at all. -________ contains 1 mole of atoms

Match the statements on the left with an appropriate response from the right. Responses on the right may be used more than once or need not be used at all. -________ contains 4 moles of H atoms

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) formula mass of CBr4(II) formula mass of P2S3

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) grams in 1 mole of SiF4(II) grams in 1 mole of AsF3

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) moles in 50 grams of N2(II) moles in 50 grams of H2S

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) molecules in 3 moles of SO2(II) molecules in 3 moles of SO3

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) atoms in 2 moles of NO2(II) atoms in 2 moles of N2O

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) molecules in 28 grams of Cl2(II) molecules in 28 grams of NaCl

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) moles of N atoms in 34 g NH3(II) moles of N atoms in 28 g of N2

Contrast the two members of each pair in the statements on the left, and then select your response from the response list on the right. -________(I) moles of O atoms in Avogadro's number of SO2 molecules(II) moles of O atoms in twice Avogadro's number of CO molecule