How many joules of heat energy are released when 50.0 g of water are cooled from 70.00C to 60.00C?

2090 joules are released.

Explanation:

Calorimetry is applied to this problem:

Q = m . C . (Final T° - Initial T°)

C is the Specific Heat, a constant for each substance, that determines the heat per unit mass, which is required to raise one degree Celsius.

C for water is 4.18 kJ /kg.°C

We convert the mass of water to kg

50 g . 1kg / 1000 g = 0.05 kg

Let's replace data in the formula:

Q = 0.05 kg . 4.18 kJ /kg.°C (60°C - 70°c)

Q = -2.09 kJ

As we have a negative value, heat is released. We need the |Q| for the value

2.09 kJ . 1000 J /kJ = 2090 joules

it is the most commonly accepted one