Moles And Molar Mass Test Questions And Answers

1. Calculate the number of moles of H2 in 10 grams of H2.

3 moles

5 moles

0.5 moles

5.5 moles

To calculate the number of moles of a substance, we need to use the formula: moles = mass / molar mass. The molar mass of H2 is 2 g/mol. Therefore, the number of moles of H2 in 10 grams can be calculated as 10 g / 2 g/mol = 5 moles.

Explanation

To calculate the number of moles of a substance, we need to use the formula: moles = mass / molar mass. The molar mass of H2 is 2 g/mol. Therefore, the number of moles of H2 in 10 grams can be calculated as 10 g / 2 g/mol = 5 moles.

2. Find the molar mass of AlCl_3.

97g/mol

97g

133.5g/mol

133.5g

The molar mass of a compound is the mass of one mole of that compound. In this case, AlCl3 is composed of one aluminum atom (Al) and three chlorine atoms (Cl). The atomic mass of aluminum is 26.98 g/mol, and the atomic mass of chlorine is 35.45 g/mol. Therefore, the molar mass of AlCl3 can be calculated as follows:

(1 × 26.98 g/mol) + (3 × 35.45 g/mol) = 133.5 g/mol

Explanation

The molar mass of a compound is the mass of one mole of that compound. In this case, AlCl3 is composed of one aluminum atom (Al) and three chlorine atoms (Cl). The atomic mass of aluminum is 26.98 g/mol, and the atomic mass of chlorine is 35.45 g/mol. Therefore, the molar mass of AlCl3 can be calculated as follows:

(1 × 26.98 g/mol) + (3 × 35.45 g/mol) = 133.5 g/mol

3. Which of the following would have more atoms?

1 mole of Au

1 mole of Si

1 mole of Li

None, all are equal

The number of atoms in 1 mole of any substance is determined by Avogadro's number, which is approximately 6.022 x 10^23. Since 1 mole of any substance contains the same number of atoms, regardless of the element or compound, all the options listed would have the same number of atoms. Therefore, the correct answer is that none of the options have more atoms; they are all equal.

Explanation

The number of atoms in 1 mole of any substance is determined by Avogadro's number, which is approximately 6.022 x 10^23. Since 1 mole of any substance contains the same number of atoms, regardless of the element or compound, all the options listed would have the same number of atoms. Therefore, the correct answer is that none of the options have more atoms; they are all equal.

4. Find the number of particles in 0.01 moles of sodium.

0.01 x 6.02 x 1023 particles

0.02 x 6.02 x 1023 particles

23 x 6.02 x 1023 particles

0.01 particles

The correct answer is 0.01 x 6.02 x 10^23 particles. This is because 0.01 moles of sodium is equal to 0.01 times Avogadro's number (6.02 x 10^23), which represents the number of particles in one mole of a substance. Therefore, multiplying 0.01 by 6.02 x 10^23 gives the number of particles in 0.01 moles of sodium.

Explanation

The correct answer is 0.01 x 6.02 x 10^23 particles. This is because 0.01 moles of sodium is equal to 0.01 times Avogadro's number (6.02 x 10^23), which represents the number of particles in one mole of a substance. Therefore, multiplying 0.01 by 6.02 x 10^23 gives the number of particles in 0.01 moles of sodium.

5. How many moles of hydrogen are in 1 mole of elemental Hydrogen H2?

0.01 moles

0.1 moles

1 mole

2 moles

The correct answer is 2 moles because the chemical formula for hydrogen gas is H2, which means that each molecule of hydrogen gas contains 2 atoms of hydrogen. Therefore, if we have 1 mole of H2, we have 2 moles of hydrogen atoms.

Explanation

The correct answer is 2 moles because the chemical formula for hydrogen gas is H2, which means that each molecule of hydrogen gas contains 2 atoms of hydrogen. Therefore, if we have 1 mole of H2, we have 2 moles of hydrogen atoms.

6. Find the amount of mole in 0.1g of hydrogen gas (H₂).

0.1 mol

0.13 mol

0.05 mol

0.00005 mol

The molar mass of hydrogen gas (H2) is 2 g/mol. To find the amount of moles in 0.1 g of hydrogen gas, we divide the given mass by the molar mass. Therefore, 0.1 g / 2 g/mol = 0.05 mol.

Explanation

The molar mass of hydrogen gas (H2) is 2 g/mol. To find the amount of moles in 0.1 g of hydrogen gas, we divide the given mass by the molar mass. Therefore, 0.1 g / 2 g/mol = 0.05 mol.

7. What is the mass in grams of 0.172 moles of NaHCO₃?

14.8 grams

14.4 grams

18 grams

None of the above

The molar mass of NaHCO3 is calculated by adding up the atomic masses of each element in the compound: Na (22.99 g/mol) + H (1.01 g/mol) + C (12.01 g/mol) + O (16.00 g/mol) + O (16.00 g/mol) + O (16.00 g/mol) = 84.01 g/mol. To find the mass in grams of 0.172 moles of NaHCO3, we multiply the number of moles by the molar mass: 0.172 moles x 84.01 g/mol = 14.4 grams. Therefore, the correct answer is 14.4 grams.

Explanation

The molar mass of NaHCO3 is calculated by adding up the atomic masses of each element in the compound: Na (22.99 g/mol) + H (1.01 g/mol) + C (12.01 g/mol) + O (16.00 g/mol) + O (16.00 g/mol) + O (16.00 g/mol) = 84.01 g/mol. To find the mass in grams of 0.172 moles of NaHCO3, we multiply the number of moles by the molar mass: 0.172 moles x 84.01 g/mol = 14.4 grams. Therefore, the correct answer is 14.4 grams.

8. Calculate the molar mass of calcium carbonate (CaCO₃).

72 g/mol

68.09 g/mol

69.29 g/mol

100.09 g/mol

Calculate the molar mass by summing atomic masses:

Calcium (Ca): 40.08 g/mol

Carbon (C): 12.01 g/mol

Oxygen (O₃): 3 × 16.00 = 48.00 g/mol

Total = 40.08 + 12.01 + 48.00 = 100.09 g/mol

Explanation

Calculate the molar mass by summing atomic masses:

Calcium (Ca): 40.08 g/mol

Carbon (C): 12.01 g/mol

Oxygen (O₃): 3 × 16.00 = 48.00 g/mol

Total = 40.08 + 12.01 + 48.00 = 100.09 g/mol

9. Calculate the molar mass of Cr₄(P₂O₇)₃.

728.8 g/mol

727.9 g/mol

729.8 g/mol

726.8 g/mol

To calculate the molar mass of Cr4(P2O7)3, we need to sum the atomic masses of all the atoms in the compound.

Chromium (Cr):

Atomic mass of Cr = 51.996 g/mol

There are 4 Cr atoms, so 4 * 51.996 g/mol = 207.984 g/mol

Phosphorus (P):

Atomic mass of P = 30.974 g/mol

There are 6 P atoms (2 in each P2O7, and there are 3 P2O7 groups), so 6 * 30.974 g/mol = 185.844 g/mol

Oxygen (O):

Atomic mass of O = 15.999 g/mol

There are 21 O atoms (7 in each P2O7, and there are 3 P2O7 groups), so 21 * 15.999 g/mol = 335.979 g/mol

Now, add the masses of all the elements:

207.984 g/mol + 185.844 g/mol + 335.979 g/mol = 729.807 g/mol

Therefore, the molar mass of Cr4(P2O7)3 is 729.807 g/mol.

Explanation

To calculate the molar mass of Cr4(P2O7)3, we need to sum the atomic masses of all the atoms in the compound.

Chromium (Cr):

Atomic mass of Cr = 51.996 g/mol

There are 4 Cr atoms, so 4 * 51.996 g/mol = 207.984 g/mol

Phosphorus (P):

Atomic mass of P = 30.974 g/mol

There are 6 P atoms (2 in each P2O7, and there are 3 P2O7 groups), so 6 * 30.974 g/mol = 185.844 g/mol

Oxygen (O):

Atomic mass of O = 15.999 g/mol

There are 21 O atoms (7 in each P2O7, and there are 3 P2O7 groups), so 21 * 15.999 g/mol = 335.979 g/mol

Now, add the masses of all the elements:

207.984 g/mol + 185.844 g/mol + 335.979 g/mol = 729.807 g/mol

Therefore, the molar mass of Cr4(P2O7)3 is 729.807 g/mol.

10. Find the mass of 0.01mol of hydrogen gas (H₂).

0.01 g/mol

0.01g

0.02 g/mol

0.02g

The mass of 0.01 mol of hydrogen gas (H2) is 0.02g. This is because the molar mass of H2 is 2 g/mol (1 g/mol for each hydrogen atom), so multiplying the molar mass by the number of moles gives the mass. In this case, 0.01 mol multiplied by 2 g/mol equals 0.02g. Therefore, the correct answer is 0.02g.

Explanation

The mass of 0.01 mol of hydrogen gas (H2) is 0.02g. This is because the molar mass of H2 is 2 g/mol (1 g/mol for each hydrogen atom), so multiplying the molar mass by the number of moles gives the mass. In this case, 0.01 mol multiplied by 2 g/mol equals 0.02g. Therefore, the correct answer is 0.02g.