Calculate the amount of heat absorbed when 70 mL of water is heated from 30°C to 70°C. The specific heat of liquid water is 4.184 J/g °C. The density of water is about 1 g/mL. Report your answer in kJ to one decimal place.

Respuesta :

Answer:

the heat absorbed by water is Q=11715.2 J

Explanation:

the amount of heat absorbed is

Q = m * c * (T - Ti)

where

Q= heat absorbed by water

m = mass f water heated

c = specific heat of water

T= final temperature , Ti= inicial temperature

also we know that the mass is related with the density through

density = mass/volume

d = m / V → m = d * V

replacing m in the heat equation

Q = m * c * (T - Ti) =  d * V * c * (T - Ti)

replacing values

Q = d * V * c * (T - Ti) = 1 g/ml * 70 ml * 4.184 J/g°C * (70°C - 30°C) = 11715.2 J

Note:

we assume

- constant density of the water between 30° and 70°

- constant specific heat of water between 30° and 70°

- the water has no impurities

To raise the temperature of 70 mL of water from 30 °C to 70 °C, 11.7 kJ of heat must be absorbed.

First, we will convert 70 mL of water to grams using its density (1 g/mL).

[tex]70 mL \times 1 g/mL = 70 g[/tex]

We want to calculate the amount of heat (q) required to raise the temperature of 70 g of water from 30 °C to 70 °C.

We will use the following expression.

[tex]q = c \times m \times \Delta T = \frac{4.184 J}{g\° C } \times 70 g \times (70\° C-30\° C) \times \frac{1kJ}{1000J} = 11.7kJ[/tex]

where,

  • c: specific heat of water
  • m: mass of water
  • ΔT: change in the temperature

To raise the temperature of 70 mL of water from 30 °C to 70 °C, 11.7 kJ of heat must be absorbed.

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