a) J reacts with oxygen to form CO2 and H2O.
Calculating the amount of CO2 formed.
"n(CO_2)=\\frac{m(CO_2)}{M(CO_2)}"
Amount of carbon in J is equal to n(CO2):
"n(C)=n(CO_2)"
Mass of carbon in J can be calculated:
"m(C)=n(C)\\cdot M(C) = n(CO_2)\\cdot M(C)=\\frac{m(CO_2)}{M(CO_2)} \\cdot M(C) =\\frac{0.872 g}{44\\frac{g}{mol}}\\cdot 12\\frac{g}{mol}=0.2378g"
Percentage by mass of carbon in J is:
"\\omega (C) = \\frac{m(C)}{m(J)}=\\frac{0.2378g}{1.30g}=0.1829 \\ or \\ 18.29 \\%"
Calculating similar way percentage by mass of hydrogen in J taking into account that amount of hydrogen in J is twice the amount of water: "n(H)=2n(H_2O)"
"\\omega (H) = \\frac{m(H)}{m(J)}=\\frac{n(H)\\cdot M(H) }{m(J)}=\\frac{2n(H_2O)\\cdot M(H) }{m(J)}=\\frac{2m(H_2O)\\cdot M(H) }{M(H_2O) \\cdot m(J)}=\\frac{2\\cdot 0.089g \\cdot 1\\frac{g}{mol} }{18\\frac{g}{mol} \\cdot 1.30g}=0.0076 \\ or \\ 0.76 \\%"
b) Knowing the mass of AgCl precipitate we are able to calculate amount of AgCl that equals to amount of Cl in J:
"n(Cl)=n(AgCl)=\\frac{m(AgCl)}{M(AgCl)}= \\frac{1.75g}{143.5\\frac{g}{mol}}=0.0122 mol"
Thus mass of chlorine in J is "m(Cl)=n(Cl) \\cdot M(Cl) = 0.4331 g"
Percentage by mass of chlorine in J is:
"\\omega (Cl) = \\frac{m(Cl)}{m(J)}=\\frac{0.4331g}{0.535g}=0.8095 \\ or \\ 80.95 \\%"
c) Empirical formula of J is CxHyClz. We can find ratios of x:y:z using percentages by mass of the elements:
"x:y:z=\\frac{\\omega (C)}{M(C)}:\\frac{\\omega (H)}{M(H)}:\\frac{\\omega (Cl)}{M(Cl)}=\\frac{0.1829}{12}:\\frac{0.0076}{1}:\\frac{0.8095}{35.5}=0.0152:0.0076:0.0228=2:1:3"
Thus empirical formula of J is C2HCl3
Checking molar mass of J: M(C2HCl3)=131.5 g/mol that corresponds to given value. Thus molecular formula of J is C2HCl3. Name of compound is 1,1,2-trichloroethylene.
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