How many Joules are required to heat 2 L of water in a pot from 20 ◦C to the boiling point of water? The specific heat of water is 4.18 J g · ◦ C and the density of water is 1 g/mL. 1. 1.7 × 105 J 2. 3.8 × 105 J 3. 6.7 × 105 J 4. 6.7 × 102 J 5. 3.8 × 104 J

Option 3 → 6.7×10⁵ J

Explanation:

We need to apply the Calorimetry formula to solve this:

Q = m . C . ΔT where:

Q is heat, m is mass, C the specific heat and ΔT → (Final T° - Initial T°)  

Let's replace data given:

By density we can determine water's mass.

1 g/mL = water's mass / 2000 mL → water mass = 2000 g

(Note: we convert the volume from L to mL)

Q = 2000 g . 4.18 J/g°C . (100°C - 20°C)

Q = 668800 J ≅ 6.7×10⁵ J

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