Mole Calculations

What is the percent by mass of oxygen in MgO? (Mg =24, O=16).

• 20%

• 40%

• 50%

• 60%

What is the percent composition by mass of oxygen in the compound MgSO₄ (molar mass = 120 g/mol, Mg =24, O=16)?

• 20%

• 27%

• 46%

• 53%

Which pair has the same empirical formula?

• NaCrO₄ and Na₂Cr₂O₇

• C₂H₄O₂ and C₆H₁₂O₆

• C₃H₆O₃ and C₂H₆O₂

• CH₄ and C₂H₆

A compound consists of 72.2% magnesium(Mg) and 27.8% nitrogen(N) by mass. What is the empirical formula?

• Mg₄N₃

• MgN₂

• Mg₃N₂

• MgN

A formula with the lowest whole # ratio of elements in a compound is called

• molecular formula

• chemical formula

• empirical formula

• condensed formula

A chemical formula that shows the actual # and kinds of atoms present in one molecule of a compound is called_________

• ionic formula

• covalent formula

• empirical formula

• molecular formula

How many grams are in 1.2 x 10²⁴ molecules of CO? (C=12, O=16)

• 28 grams

• 56 grams

• 6.02 grams

• 1.2 grams

f an atom of Fluorine has an atomic mass of 19 amu, it has a Molar mass of ____

• 19 lbs.

• 19 kg

• 19 g/mol

• 19 mols

Which of the following statements regarding the mole is INCORRECT?

• A mole is a unit of quantity equal to 6.02 x 10²³ particles.

• The number of particles in a mole is known as Avogadro’s number.

• A mole of particles of an element is numerically equal to the atomic mass of the element.

• none of the above

The mass of one mole of an element is equal to

• its atomic number from the periodic table, but in amus.

• its atomic mass from the periodic table, but in amus.

• its atomic number from the periodic table, but in grams.

• its atomic mass from the periodic table, but in grams.