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How many kilojoules are required to change the temperature of 20.0 g of H2O from 20 Celsius to steam at 100 Celsius.

User Mardon
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1 Answer

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20 votes

Answer

45.36372 kilojoules

Step-by-step explanation

Given:

Mass of H2O = 20.0 g

Initial temperature, T₁ = 20 °C

Final temperature, T₂ = 100 °C

Change in temperature, ΔT = T₂ - T₁ = 100 °C - 20 °C = 80 °C

Specific heat of water, c = 4.186 J/g°C

What to find:

The kilojoules required to change the temperature of 20.0 g of H2O from 20 Celsius to steam at 100 Celsius.

Step-by-step solution:

For this problem, there are only two heats to consider:

q₁ = heat required to warm the water from 20.0 °C to 100.0 °C.

q₂ = heat required to vapourize the water to steam at 100 °C.

q₁ = mcΔT = 20.0 g x 4.186 J/g°C x 80 °C = 163.72 joules

q₂ = mΔHvap = 20.0 g x 2260J/g = 45200 joules

Therefore, q₁ + q₂ = (163.72 + 45200)J = 45363.72 J = 45.36372 kJ.

Thus, 45.36372 kilojoules are required to change the temperature of 20.0 g of H2O from 20 Celsius to steam at 100 Celsius.

User David Ibrahim
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