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WAEC Physics 2015 Paper
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© africaexams.com
Question : 18
Total: 50
A quantity of hot water at 100
o
C is added to 400g of water at 10
o
C until the temperature of the mixture is 60
o
C.
Calculate the mass of the hot water added. [Specific heat capacity of water =4200JKg
-1
K
-1
]
200g
320g
400g
500g
Validate
Solution:
Heat lost by hot water = Heat gained by cold water
M x 4200 x (100 - 60 = 0.4 x 4200 x (60 - 10)
4200m x 40 = 0.4 x 4200 x 50
40m = 0.4 x 50
m =
0.4
×
50
40
= 0.5kg
= 500g
© africaexams.com
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