When entering coefficients to balance equations, recall that just writing the symbol implies "1." therefore, if a coefficient of "1" is required, choose "blank" for that box. balance the following equation. 2c2h2 + o2→ 4co2 + h2o

The Equation given in statement is as follow,

                              2 C₂H₂  +  O₂     →    4 CO₂  +  H₂O

According to equation,

Carbon atoms on reactant side are 4 in number, and that on product side are also 4 in number. SO, carbon atoms are balanced.

Hydrogen atoms on reactant side are 4, and on product side are 2. Means Hydrogen atoms are not balance. So, to balance them multiply H₂O with 2. So,
                              2 C₂H₂  +  O₂     →    4 CO₂  +  2 H₂O

Now, calculate number of Oxygen atoms on both sides. There are 2 Oxygen atoms on reactant side and 10 Oxygen atoms on product side. So, to balance them multiply O₂ on reactant side with 5. So,

                              2 C₂H₂  +  5 O₂     →    4 CO₂  +  2 H₂O

Above Equation is balanced.