Chemistry Spring Semester Exam 23-24

What is the total number of atoms in 1 mole of NH₃?

• 17.04 atoms

• 2 atoms

• 6.02X10²³ atoms

• 1.03X10²⁵ atoms

What is the molar mass of C₂H₆?

• 30.08 g/mol

• 31 moles

• 13.02 g

• 6.02X10²³ molecules

What is the mass of Oxygen if you have 4 moles of Oxygen? (Reminder this is a diatomic element)

• 60 g/mol

• 135 g/mol

• 128 g/mol

• 71 g/mol

What is the number of moles in 25 grams of CaCO₃?

• 1 mole

• 2 mole

• 0.1 mole

• 0.2 mole

What is the percent by mass of carbon in acetone, C3H6O?

• 20.7%

• 30.0%

• 1.61%

• 62.1%

Calculate the percent composition of calcium acetate, Ca(C2H3O2)2.

• 40.0% Ca; 48.0% C; 4.0% H; 64.0% O

• 25.4% Ca; 30.4% C; 3.8% H; 40.5% O

• 25.0% Ca; 25.0% C; 4.5% H; 45.5% O

• 21.1% Ca; 30.0% C; 7.8% H; 42.1% O

What calculations can you perform if you know the molar mass of a compound?

• Converting moles of a compound to grams

• Converting grams of the compound to moles

• Both A and B

• Neither A nor B

To determine the formula of a new substance, one of the first steps is to find the

• volume at STP.

• percent composition.

• molar mass.

• number of particles per mole.

If 20.0 grams of Ca combines completely with 16.0 grams of S to form a compound, what is the percent composition of Ca in the compound?

• 1.25%

• 55.6%

• 20.0%

• 44.4%

If 60.2 grams of Hg combines completely with 24.0 grams of Br to form a compound, what is the percent composition of Hg in the compound?

• 28.5%

• 60.1%

• 71.5%

• 39.9%