Question

A 50.51g sample of a compound made from phosphorus and chlorine is decomposed. Analysis of the products showed that 11.39 g of phosphorus atoms were produced. Answer using three significant figures.

What is the percent by mass of phosphorus?
%

What is the percent by mass of chlorine?
%

Answer 1

mass of phosphorus (P) = 11.39g

mass of chlorine (CL)  =  mass of compound - mass of phosphorus

                                         50.51 - 11.39 = 39.12g

atomic mass of P : CL  =    ( 11.39 / 31 ) :  (39.12 / 35.5)  =  1  :   3

mass of p%  =   11.39/31 * 100 =    36.7 %

mass of CL%  =   39.12 / 35.5 * 100=  110 %

empirical formula :-  PCl3

Answer 2

Answer:

The percent by mass of phosphorus is 22.5%.

The percent by mass of chlorine is 77.5%.

Explanation:

Amount of compound made from phosphorus and chlorine, M = 50.51 g

Amount of  phosphorus atoms were produced,x = 11.39 g

$\%=\frac{\text{Amount of element's atoms in compound}}{\text{Amount of compound}}\times 100$

The percent by mass of phosphorus:

$\%=\frac{x}{M}\tims 100=\frac{11.39 g}{50.51 g}=22.5\%$

The percent by mass of chlorine:

= 100% - (percent by mass of phosphorus)%=100 % -22.5% = 77.8 %