Anonymous
Anonymous asked in Science & MathematicsChemistry · 1 decade ago

Chemistry help please? PLEASE explain your answers, thanks!?

Hi---Could someone please help me??? I am struggling! PLEASE explain your answers so I can follow you. Thanks to all. All help is greatly appreciated! :)

Calculate each of the following:

(a)Mass of % of H in ammonium bicarbonate

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

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  • 1 decade ago
    Best answer

    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

    Add up the totals: 246.081

    Of which O is 175.989

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

  • 1 decade ago

    (a) ammonium bicarbonate has a formula of NH4HCO3.

    the molar mass of this compound is 79.07 g.

    the mass of H in the compound in grams is 5.05.

    (5.05/79.07) 100 = 6.39%

    (b) uses the same method as above

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