Final answer:
The heat released when 6.5 g of sodium hydroxide dissolves in water, raising the temperature from 21.6°C to 37.8°C, is calculated using the formula Q = mcΔT. The total heat released is approximately 7.192 kJ.
Step-by-step explanation:
To calculate the quantity of heat released when sodium hydroxide dissolves in water, we can use the formula Q = mcΔT, where 'm' is the mass of the solution, 'c' is the specific heat capacity of water, and ΔT is the change in temperature.
Firstly, we need to calculate the total mass of the solution. Since we have 6.5 g of NaOH and 100 g of water, the total mass (m) is 106.5 g. Next, the specific heat capacity (c) of water is 4.18 J/g°C, which is a constant value. The change in temperature (ΔT) is the final temperature minus the initial temperature, which in this case is 37.8°C - 21.6°C = 16.2°C.
We then plug these values into the equation to calculate the heat (Q):
Q = (106.5 g) x (4.18 J/g°C) x (16.2°C) = 7191.54 J
Since the question asks for the answer in kilojoules, we need to convert joules to kilojoules by dividing by 1,000:
Q = 7191.54 J / 1000 = 7.192 kJ
Therefore, the heat released from this reaction is approximately 7.192 kJ.