Question

How many kilograms of sour cream should be added (stirred into the water) to 0.5 litres of water at T=80°C to cool the water to 40°C, which is the ideal temperature for soup if the temperature of the sour cream (sour cream 20%) before it is added to the soup is 5°C?

Answer 1

The mass of the sour cream that should be added is 0.68 kg.

Mass of the water

Mass of the water is calculated as follows;

mass = density x volume

• density of water = 1 kg/L

mass = (1 kg/L) x 0.5 L = 0.5 kg

Conservation of energy

Heat gained by the sour cream = Heat lost by the water

$m_s c_s\Delta \theta _s = m_wc_w\Delta \theta _w\\\\m_s = \frac{m_wc_w\Delta \theta _w}{c_s\Delta \theta _s}$

where;

• Cs is specific heat of sour cream
• Cw is specific heat of water
• Δθ is change in temperature

$m_s = \frac{0.5 \times 4184 \times (80 - 40)}{3510 \times (40 - 5)} \\\\m_s = 0.68 \ kg$

Learn more about heat capacity here: https://brainly.com/question/16559442