p19_027.pdf

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Chapter 19 - 19.27

T i ), where Q is the heat added, m is the mass of the

sample, T i is the initial temperature, and T f is the ﬁnal temperature. Thus, recalling that a change

in Celsius degrees is equal to the corresponding change on the Kelvin scale,

c =

314J

25 . 0 ◦ C) = 523 J / kg

·

K .

(30 . 0

×

10 − 3 kg)(45 . 0 ◦ C

−

(b) The molar speciﬁc heat is given by

c m =

Q

N ( T f −

T i ) =

314J

(0 . 600mol)(45 . 0 ◦ C

−

25 . 0 ◦ C) =26 . 2J / mol

·

K .

(c) If N is the number of moles of the substance and M is the mass per mole, then m = NM ,so

N = m

M =

30 . 0

10 − 3 kg / mol =0 . 600 mol .

×

10 − 3 kg

50

×

27. (a) The speciﬁc heat is given by c = Q/m ( T f −