Chemical Math Review

Front

What is the percent composition of Cu in Cu2S?

Back

%Cu = 79.854

Front

What is the percent composition of S in Cu2S?

Back

%S = 20.145

Front

Balance the equation: _AlBr3 + _K2SO4 → _KBr + _Al2(SO4)3

Back

2 AlBr3 + 3 K2SO4 → 6 KBr + 1 Al2(SO4)3

Front

What percentage of the total atomic mass of magnesium bromide (MgBr2) is composed of magnesium?

Back

13%

Front

Which pair has the same empirical formula: NaCrO4 and Na2Cr2O7, or C2H4O2 and C6H12O6?

Back

C2H4O2 and C6H12O6

Front

Balance the equation: _AgNO3 + _Cu → _Cu(NO3)2 + _Ag

Back

2 AgNO3 + 1 Cu → 1 Cu(NO3)2 + 2 Ag

Front

Define empirical formula.

Back

An empirical formula shows the simplest whole-number ratio of elements in a compound.

Front

What is the molecular formula of a compound?

Back

A molecular formula shows the actual number of atoms of each element in a molecule.

Front

How do you calculate percent composition?

Back

Percent composition = (mass of element in 1 mole of compound / molar mass of compound) × 100%.

Front

What is the molar mass of MgBr2?

Back

Molar mass = 24.305 (Mg) + 2 × 79.904 (Br) = 24.305 + 159.808 = 184.113 g/mol.