Determining Molar Mass

What is the molar mass of AuCl₃?

• 96 g

• 130 g

• 232.5 g

• 303.3 g

Answer explanation

To find the molar mass of AuCl3, add the molar mass of gold (Au, 197 g/mol) and three times the molar mass of chlorine (Cl, 35.5 g/mol). This gives 197 + 3(35.5) = 303.3 g, making 303.3 g the correct answer.

Mass of 1 mole of Cs₂SO₄

• 361.9

• 361.8

• 313.9

• 180

Answer explanation

To find the mass of 1 mole of Cs2SO4, sum the atomic masses: Cs (132.9) x 2 + S (32.1) + O (16) x 4 = 361.9 g/mol. Thus, the correct answer is 361.9.

Determine the gram formula mass of H₂O₂?

• 18 g/mol

• 34 g/mol

• 8 g/mol

• 1 g/mol

Answer explanation

The gram formula mass of H2O2 (hydrogen peroxide) is calculated as follows: 2 H (1 g/mol each) + 2 O (16 g/mol each) = 2 + 32 = 34 g/mol. Therefore, the correct answer is 34 g/mol.

Determine the GFM of CaCl₂?

• 111 g/mol

• 115.5 g/mol

• 3 g/mol

• 54 g/mol

Answer explanation

To find the GFM of CaCl2, add the atomic masses: Ca (40.08 g/mol) + 2 x Cl (35.45 g/mol) = 40.08 + 70.90 = 110.98 g/mol, rounded to 111 g/mol. Thus, the correct answer is 111 g/mol.

Which has more atoms? 1 mole of KCl or 1 mole of LiCl?

• KCl

• LiCl

• they are the same

Answer explanation

1 mole of KCl and 1 mole of LiCl both contain the same number of formula units, which is Avogadro's number (approximately 6.022 x 10^23). Therefore, they have the same total number of atoms.

Which has more mass 1 mol of KCl or 1 mol of LiCl?

• KCl

• LiCl

• they are the same

Answer explanation

1 mol of KCl has a molar mass of about 74.55 g/mol, while 1 mol of LiCl has a molar mass of about 42.39 g/mol. Therefore, KCl has more mass than LiCl.

How do you determine the mass of 1 mole of an atom?

• Guess

• Weigh it on the scale

• Look at the atomic number (bottom left)

• Look at the atomic mass number (top left)

Answer explanation

To determine the mass of 1 mole of an atom, you look at the atomic mass number (top left) on the periodic table, which indicates the mass in grams of one mole of that element.

What is the definition of a mole?

• 12 of something

• 6.02 x 10^23 of something

• 1 of something

• 1 gram of something

Answer explanation

A mole is defined as 6.02 x 10^23 of something, known as Avogadro's number. This value represents the number of particles, such as atoms or molecules, in one mole of a substance, making it a fundamental concept in chemistry.

• 82 amu

• 98 amu

• 104 amu

• 62 amu

Answer explanation

To find the gram formula mass of H2SO4, add the atomic masses: H (1 amu x 2) + S (32 amu) + O (16 amu x 4) = 2 + 32 + 64 = 98 amu. Thus, the correct answer is 98 amu.

What are the units for gram formula mass?

• moles

• grams

• amu

• picometers

Answer explanation

The gram formula mass is expressed in atomic mass units (amu), which reflects the mass of one mole of a substance in grams. Therefore, the correct unit for gram formula mass is amu.