23 Prep Composition Stoichiometry

What is the percent by mass of oxygen in MgO?

• 20%
• 40%
• 50%
• 60%

What is the percent composition by mass of magnesium in the compound MgSO₄?

• 20%
• 27%
• 46%
• 53%

Rust is a compound of iron and oxygen. If in a 48.0 g piece of rust, there are 14.4 g of oxygen. What is the mass of iron in the sample?

• 33.6 g iron

• 62.4 g iron

• 3.33 g iron

• 0.300 g iron

What is the percent composition of aluminum phosphate?….. :-) You get to figure out the formula.

• Al = 25% P = 25% O = 75%

• Al = 22.1% P = 35.8% O = 42.1%

• Al = 14.3% P = 25.4% O = 60.3%

• Al = 22.1% P = 25.4% O = 52.5%

What is the mass of one mole of aluminum?

• 27.00 g

• 26.00 g

• 54.90 g

• 13 g

Calculate the molar mass for Al(OH)₃

• 78.00 g/mol

• 72.10 g/mol

• 28.00 g/mol

• 25.01 g/mol

Molar mass is in units of ________.

• grams
• grams/mole
• mole
• moles/gram

What is the Molar Mass of Potassium Sulfide?..... :-) You get to figure out the formula.

• 110.262 g/mol

• 71.164 g/mol

• 174.258 g/mol

• 158.259 g/mol

How do I calculate the molar mass of a compound?

• It is always 6.02 x 10²³

• Find the atomic mass of every element in total and add them together

• It is always 1

• Number of moles x mass

What is the definition of molar mass?

• number of grams per one mole of a substance
• whole number ratio that is a multiple of a chemical formula
• simplest, whole number ratio of a chemical formula
• 6.02 x 10^23 particles per one mole of a substance