Chapter 5: Thermodynamics Worksheet With Answers - Ap Chemistry 2015-2016 (Page 5 of 14) in pdf

Chapter 5: Thermodynamics Worksheet With Answers - Ap Chemistry 2015-2016 Page 5

3. What a mount o f h eat i s r eleased w hen 1 75 g o f w ater c ools f rom 1 00.°C t o r oom t emperature, 2 0.0

°C?

58600 J

4. We d on’t a lways h ave t o w arm u p o r c ool d own w ater. T he s pecific h eat c apacity o f c opper m etal i s

0.39 J /g·°C. I t i s _ ____________ ( easier/more d ifficult) t o h eat u p c opper t han t o h eat u p w ater.

How m uch e nergy w ould i t t ake t o h eat u p a 5 .20 g s ample o f c opper f rom 2 0.0 ° C t o 1 00.°C?

162 J

5. If 3 00. J o f h eat e nergy w ere u sed t o h eat u p a 5 .00 g ram s ample o f c opper m etal a nd a 5 .00 g ram

sample o f w ater b oth s tarting a t 1 0.0°C, c alculate t he f inal t emperature o f e ach s ample?

Water: 2 4.3˚C; C opper: 1 64˚C

Signs o f Δ T a nd q :

− q m eans h eat i s r eleased. + q m eans h eat i s a bsorbed.

ΔT i s a lways f inal t emperature – i nitial t emperature.

If s omething i s g etting h otter ( 10° → 3 0°) t he Δ T i s 3 0 – 1 0 = + 2 0°. ( heat i s a bsorbed)

If s omething i s g etting c ooler ( 75° → 2 5°) t he Δ T i s 2 5 – 7 5 = − 5 0°. ( heat i s r eleased)

6. Suppose w e m ix 9 0.0 g rams o f h ot w ater ( 90.0°C) w ith 1 0.0 g rams o f c old w ater ( 10.0°C).

Let x = t he f inal t emperature. C = 4 .184 J /g·°C

a. S et u p a n e xpression f or t he e nergy r eleased ( q) b y t he h ot w ater ( Δq

= m

CΔT

)

hot

q = 9 0*4.184*∆T; q = 9 0*4.184*(T

-‐‑ 9 0)

b. S et u p a n e xpression f or t he e nergy a bsorbed ( q) b y t he c old w ater ( Δq

= m

CΔT

)

cold

q = 1 0*4.184*(T

-‐‑ 1 0)

c. Knowing t hat t he h eat r eleased = − h eat a bsorbed, c ombine t he t wo e xpressions a nd s olve f or x .

82˚C

7. We d on’t a lways h ave t o u se w ater. L et’s u se s ome a luminum s hot ( pellets). 1 75 g rams o f h ot

aluminum ( 100.°C) i s d ropped i nto a n i nsulated c up t hat c ontains 4 0.0 m L o f i ce c old w ater ( 0.0°C).

Follow t he e xample a bove t o d etermine t he f inal t emperature, x .

a. S et u p a n e xpression f or t he h eat l ost b y t he a luminum ( C=0.900 J /g·°C)

b. S et u p a n e xpression f or t he h eat g ained b y t he c old w ater.

c. Put t he t wo e xpressions t ogether ( don’t f orget t o c hange o ne o f t he s igns) a nd s olve f or x .

48˚C

Chapter 5: Thermodynamics Worksheet With Answers - Ap Chemistry 2015-2016 Page 5