use the formula q=mc(deta t)
where q = the energy require to raise a certain amount of a substance to a certain temperature
m = mass of the substance in kg
c = specific heat (unit J/K.kg)
deta t = changing in temperature ( can be in Kelvin or C because it is the change of temperature)
We should look at the unit of c, it has J not kJ.
So we convert unit while doing the calculation: so c = (21.kJ * 1000 J/kJ)/ [(67.2oC-59.9oC)*697.0g/1000g/kg) = 4127.277373 J/K.kg
ok, now how many sig fig to report? Look at all of the number the problem gives you and find out which one has the least sig fig and how many sig fig they are:
21.kJ = 2 sig fig
67.2 and 59.9 = 3 sig fig
697.0 g = 4 sig fig
So the final answer should contain 2 sig fig only -> 4100 J/K.kg . Note that those trailing 0 in this case with no "period" at the end do not count as sig fig.
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