Question

Please explain all work and explain the concept of combustion... I am new to this and the last time I posted this question the answer was not satisfactory. i need to understand for an exam. thx!

15. A 2.0 g sample of ethylene (C2H4, molecular weight 28.05 g/mol) is combusted in pure oxygen (O2, molecular weight 32.00 g/mol). What mass of CO2 (molecular weight 44.01 g/mol) was generated? A. 22.82 g B. 17.88 g C. 11.21 g D. 6.28 g. E. none of the above. ANSWER: D

Answer 1

In combustion reaction, compound reacts with O2 to give CO2 and H2O . Below is the combustion reaction:

C2H4 + 3 O2 ---> 2 CO2 + 2 H2O

Molar mass of C2H4 = 28.05 g/mol


mass(C2H4)= 2.0 g

use:
number of mol of C2H4,
n = mass of C2H4/molar mass of C2H4
=(2 g)/(28.05 g/mol)
= 7.13*10^-2 mol

Balanced chemical equation is:
C2H4 + 3 O2 ---> 2 CO2 + 2 H2O


Molar mass of CO = 44.01 g/mol

According to balanced equation
mol of CO2 formed = (2/1)* moles of C2H4
= (2/1)*0.0713
= 0.1426 mol


use:
mass of CO2 = number of mol * molar mass
= 0.1426*44.01
= 6.28 g
Answer: D