Determine the % yield when 7.80 grams of benzene (c6h6) burns in oxygen gas to form 3.00 grams of co2 gas and water vapor.

Benzene reacts with O₂ to produce CO₂ and H₂O, i.e.

                           C₆H₆  +  7.5 O₂    →    6 CO₂  +  3 H₂O

According to equation,

    78.11 g (1 mole) C₆H₆ reacts to produce  =  264 g (6 moles) of CO₂

Hence,

      7.80 g C₆H₆ when reacted will produce  =  X g of CO₂

Solving for X,
                                X  =  (7.80 g × 264 g) ÷ 78.11 g

                                X  =  26.36 g of CO₂

Theoretical Yield:
                             26.36 g of CO₂ produced is theoretical yield which shows 100% reaction between benzene and oxygen.

Actual Yield:
                   According to statement the actual amount of CO₂ produced is 3.0 g of CO₂.

%age Yield:
      
                %age Yield  =  (Actual Yield ÷ Theoretical Yield) × 100

Putting Values,

                %age Yield  =  (3.00 g ÷ 26.36 g) × 100

                %age Yield  =  11.38 %

They can measure  the amount of energy gained or lost

The answer is c) pyrite