Question

(a) How many moles of ammonium ions are in 0.807 g of ammonium carbonate?

(b) What is the mass, in grams, of 0.0445 mol of iron(III) phosphate?

(c) What is the mass, in grams, of 2.48 1023 molecules of aspirin, C9H8O4?

(d) What is the molar mass of a particular compound if 0.060 mol weighs 5.34 g?

Answer 1

a)

we know that

moles = mass / molar mass

so

moles of (NH4)2C03 = 0.807 / 96 = 8.40625 x 10-3

now

(NH4)2C03 ---> 2 NH4+ + C032-

so

moles of NH4+ = 2 x moles of (NH4)2C03

so

moles of NH4+ = 2 x 8.40625 x 10-3

moles of NH4+ = 0.0168125

b)

we know that

mass = moles x molar mass

so

mass of FeP04 = 0.0445 x 150.81 = 6.71

so

6.71 grams of FeP04 is present

c)

now

moles = number of molecules / 6.023 x 10^23

so

moles of aspirin = 2.48 x 10^23 / 6.023 x 10^23 = 0.41175

now

mass = moles x molar mass

so

mass of aspirin = 0.41175 x 180

mass of aspirin = 74.116

so

74.116 grams of aspirin is present

d)

now

molar mass = mass / moles

so

molar mass = 5.34 / 0.06

molar mass = 89

so

the molar mass is 89 g / mol