Question

 Acetylene gas (C2H2), used in oxy-acetylene welding, reacts with oxygen according to the following equation:

  2 C2H2           +      5 O2                            ⇒      4 CO2             +    2 H2O

f.w. 26.038           f.w.  31.9988                      f.w.  44.010         f.w.  18.015

       How many grams of acetylene were burned if 286.4 grams of CO2 were produced during the combustion reaction? (Please show the major steps of calculation)  

Answer 1

Balanced reaction

$2C_2H_2+5O_2\ \ \ \rightarrow 4CO_2+2H_2O$

Moles of CO₂ produced = ${Given \ mass \over molar \ mass} ={ \frac{286.4g}{44g}}$ =6.5 moles

By Stoichiometry we say that

2mole of acetylene produces 4 mole of CO₂

By Stoichiometry wr get

Moles of acetylene required = $6.5\over 2$

= 3.25 moles

So masd of acetylene burned

= 3.25×molar mass

=3.25×26g

=84.5 g