Moles And Molar Mass Test Questions And Answers

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

Explanation
To calculate the molar mass of CaCOH (calcium formate hydrate), we need to add up the atomic masses of each element in the compound. The molecular formula of calcium formate hydrate is Ca(HCOO)2\*H2O.
Break down the compound into its constituent elements:
Calcium (Ca): 1 atom \* 40.08 g/mol (atomic mass) = 40.08 g/mol
Formate ion (HCOO): 2 ions \* 1 atom of carbon (12.01 g/mol), 2 atoms of oxygen (2 \* 16.00 g/mol), and 1 atom of hydrogen (1.01 g/mol) = 45.02 g/mol
Water (H2O): 1 molecule \* 2 atoms of hydrogen (2 \* 1.01 g/mol) and 1 atom of oxygen (16.00 g/mol) = 18.02 g/mol
Now, add the masses of each component together:
40.08 g/mol (Ca) + 45.02 g/mol (2 HCOO) + 18.02 g/mol (H2O) = 103.12 g/mol
However, the given answer choices do not include 103.12 g/mol, which is the molar mass of Ca(HCOO)2\*H2O. Among the given answer choices, 68.09 g/mol is the closest to the correct value, but it does not correspond to the actual molar mass of CaCOH.

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.

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.

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.

Explanation
The molar mass of Cr4(P2O7)3 can be calculated by adding up the atomic masses of all the atoms in the compound. Chromium (Cr) has an atomic mass of approximately 52 g/mol, phosphorus (P) has an atomic mass of approximately 31 g/mol, and oxygen (O) has an atomic mass of approximately 16 g/mol. The compound has 4 chromium atoms, 6 phosphorus atoms, and 21 oxygen atoms. Therefore, the molar mass is calculated as follows: (4 * 52) + (6 * 2 * 31) + (21 * 7 * 16) = 729.8 g/mol.

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.

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.

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.

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.