When 200 grams of water cools from 50.°c to 25°c, the total amount of heat energy released by the water is?

21 kJ  

Step-by-step explanation:

The formula for the heat q is

q = mCΔT

Data:

m = 200 g; C = 4.184 J·°C⁻¹g⁻¹

T₁ = 50. °C; T₂ = 25 °C

Calculations:

ΔT = T₂ - T₁

ΔT = 25 – 50.

ΔT = -25 °C

q = 200 × 4.184 × (-25)

q = -21 000 J     Convert to kilojoules

q = -21 kJ

The negative sign shows that energy is released, so the water has released 21 kJ of energy.