A floodlight consumes 15.3 kJ of energy. It is found that it delivers only 3.9 kJ of useful light. What is the % efficiency of this floodlight?

The compound methyl butanoate smells like apples. its percent composition is 58.8% c, 9.9% h, and 31.4% o. what’s the empirical formula ?

Can someone me with questions 12 and 13 plz.

1) which of the following is the best example of a physical change? a) sugar dissolving in tea b) firefly glowing 2) in the combustion of ethane, what is/are the reactants? c2h6 + o2 ==> co2 + h2o a) c2h6 and o2 b) co2 and c2h6