1) Calculate the percent composition by mass (to 4 significant figure) of all th

Question

1) Calculate the percent composition by mass (to 4 significant figure) of all the elements in calcium phosphate [Ca3(PO4)2], a major component of bone

%Ca?

%P?

%O?

2) Menthol is a flavoring agent extracted from peppermint oil. It contains C,H, and O. In one combustion analysis, 10.0mg of the substance yields 11.53mg of H2O and 28.16mg of CO2. what is the empirical formula of menthol?

CHO (add the subcritps)

3) Determine the number of atoms of each element in the empirical formula of a compound with the following composition.

62.40 percent C, 9.892 percent H, 27.70 percent O

show work for all posible points

Explanation / Answer

% Ca = ( 100 x 40.078x3)/(310.18) = 38.7627 %

% P = ( 100x30.9738x2)/(310.18) = 19.9715 %

% O = 100-38.7627 -19.9715 =41.2658 %

2)   CaHbOc + O2 ---------> aCO2 + (b/2) H2O  

11.53 mg H2O = 11.53/18 = 0.6405 milli moles , 28.16 CO2 = 28.16/44 = 0.64 milli moles ,

as per eq   b =0.64x2 = 1.28, a= 0.64 , hence part of formul will be CnH2n ,

mass by Oxygen = ( 10)-( 0.64x12) -(1.28 x 1) = 1.04 mg

milli moles of oxygen = 2.192/16 = 0.137 ,

now C% = 0.64 , H = 1.28 , O = 0.137 , we divide everything by 0.137 we get

C = (0.64/0.137) = 4.5 , H = 9.34 , O = 1 ,

emperical formula is (C9H18O2)n

3) atoms of C = 6.023x10^ 23 x ( 62.4/12) = 3.132 x10^ 24

H atoms = 6.023x10^ 23 x (9.892/1) = 5.958 x10^ 24

O atoms = 6.023x10^ 23 x ( 27.7/16) = 1.0427 x10^ 24

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