3. A 0.500 kg pot of hot water for tea has cooled to 40.0 OC. How much freshly boiled water must be added (at 100 OC) to raise the temperature of the tea water to a respectable 65.0 OC?
Let n represent the unknown mass of water to be added.
Old mass + new mass = total mass
40c x 0.5 kg + 100c x n = 65 (0.5kg + n)
20 kg + 100 n = (32.5kg + 65n)
52.5 kg = 165 n
1 kg = 3.1n
n = 1/3.1
n = 0.32 kg
To raise the temperature of the tea to 65 degrees, 0.32kg of 100c water must be added.