Molar Mass Percent Composition



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Honors Chemistry

Percent Composition Worksheet

Calculate the percentage composition of each of the following compounds. Show your work and always include units (Show the answer from calculator first, then round the answers to 2 decimal places).

1. Ca3P2 (66.0% Ca, 34.0% P) % Ca = 120.24 x 100% % P = 61.94_ x 100%

182.15 182.15

MM of Ca3P2:

= 66.00065869 % = 33.9993413%

3 (Ca) = 3 (40.08) = 120.24

2 (P) = 2 (30.97) = 61.94_ = 66.00 % Ca = 34.00% P

182.15 g/mol

Ca3P2 Checking: 66.00 % + 34.00% = 100.00%

2. Ca(OH)2 (54.1% Ca, 43.2% O, 2.7% H)

3. Na2SO4 (32.4% Na, 22.6% S, 45.0% O)

4. CaSO4 (29.4% Ca, 23.6% S, 47.0% O)

5. (NH4) 2SO4 (21.2% N, 6.1% H, 24.3% S, 48.4% O)

6. Zn3(PO4)2 (50.8% Zn, 16.1% P, 33.1 % O)

7. Mg(NO3)2 (16 % Mg, 18 % N, 64 % O)

8. CrF3 (48% Cr, 52% F) 9. Na3PO4 (42 % Na, 19% P, 39% O)

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(From MM)

Never Use 100% - ____%

1) Round to 2 decimal places

2) Checking: Add up all % (99.99% -100.01 %)

% composition MM of Ele x 100%

Of each element = MM of Cpd

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