Question

If given a quantity in grams, and the name of a compound, then . . . .

How many moles of calcium nitrate?

How many moles of Ca, N and O?

How many formula units of each?

How many of each type of atom?

How many grams of each element?

What is the % composition (% mass) of each element?

37.6 g of calcium nitrate

Answer 1

mass = 37.6 g

Calcium nitrate = Ca(NO3)2 = 164.088 g /mol.

1) moles = mass / molar mass = 37.6 / 164.088 = 0.229

moles of Ca(NO3)2 = 0.229

2) moles of Ca = 0.299

moles of N = 2 x 0.229 = 0.458

moles of O = 6 x 0.229 = 1.374

Formula = Ca(NO3)2

moles of formula units = 0.229

moles of Ca = 0.229

moles of N = 2 x 0.229 = 0.458

moles of O = 6 x 0.229 = 1.374

mass of Ca = 0.229 x 40.08 = 9.178 g

mass of N = 0.458 x 14 = 6.412 g

mass of O = 1.374 x 16 = 21.98 g

% mass of Ca =(9.178 / 37.6) x 100

% mass of N = (6.412 / 37.6) x 100

% mass of N = 17.05

% mass of O = (21.98 / 37.6) x 100

% mass of O = 58.46