Anonymous

Calculate each of the following:

(a)Mass of % of H in ammonium bicarbonate

(b) Mass of % of O in sodium dihydrogen phosphate heptahydrate

Relevance

First : write the molecukar formula for ammonium bicarbonate: This is probably better called ammonium hydrogen carbonate:

NH4HCO3

Now calculate the molar mass of NH4HCO3

Count how many of each element you have:

N =1

H = 5

C = 1

O = 3

Use the periodic table to get the atomic mass of each element:Then multiply this atomic mass by the number above:

N = 14.007*1 = 14.007

H = 1.008*5 = 5.040

C = 12.011*1 = 12.011

O = 15.999*3 = 47.997

Add up all the totals: 14.007+5.040+12.011+47.997 = 79.055g/mol

From these figures you can see that in 79.055g of NH4HCO3 you have 5.040g H

%H = 5.040/79.055*100 = 6.375

Mass % of H in NH4HCO3 = 6.38%

The molecular formula for sodium hihydrogen phosphate heptahydrate is: NaH2PO4.7H2O

The tricky part here is to realise that 7H2O is 14H and 7O

Now do exactly as was done above:

Write down the number of each element:

Na = 1

H = 2+14 = 16

P = 1

O = 4+7 = 11

Use the periodic table to get the atomic mass of each element:Then multiply this atomic mass by the number above:

Na = 22.990 *1 = 22.990

H = 1.008*16 = 16.128

P = 30.974 *1 = 30.974

O = 15.999*11 = 175.989

Of which O is 175.989

%O in NaH2PO4.7H2O = 175.989/246.081*100 = 71.5%