if the combustion of oil yields 4.0x10^4 kj/kg what mass of oil must be burned to yield the number of joules in part b? the answer i got in part b was 7.70 x10^11 J and that it right. for this problem i divided the answer i got 7.70x10^11 by 4.0x10^4 and changed the 4.0x10^4 to joules and then multiplied by 1 kj but i didn't get the right answer.
To solve this problem correctly, let's first convert the given energy in kilojoules to joules.
You correctly determined the energy yield from the combustion of oil as 4.0x10^4 kJ/kg. To convert this to joules, we need to multiply it by 1000 (since there are 1000 joules in 1 kilojoule).
So, 4.0x10^4 kJ/kg = 4.0x10^4 kJ/kg * 1000 J/kJ = 4.0x10^7 J/kg.
Now, you mentioned that the answer in part b is 7.70x10^11 J. To find the mass of oil that must be burned to yield this amount of energy, we need to divide the energy (in joules) by the energy yield per kilogram.
So, the mass of oil (in kilograms) = 7.70x10^11 J / (4.0x10^7 J/kg).
Now, let's divide the numbers:
mass of oil = (7.70x10^11 J) / (4.0x10^7 J/kg)
= 7.70x10^11 J / 4.0x10^7 J/kg.
When dividing the numbers with the same base, we subtract the exponents:
mass of oil = 7.70x10^(11-7) kg
= 7.70x10^4 kg.
Therefore, the mass of oil that must be burned to yield 7.70x10^11 J is 7.70x10^4 kg.