Calculate the quantity of heat needed to change the temperature of 60g of ice at...

PHYSICS
WAEC 2019

Calculate the quantity of heat needed to change the temperature of 60g of ice at 0 °C to 80 °C. [specific latent heat of fusion of ice= 3.36 x 10\(^5\) Jkg\(^{-1}\) specific heat capacity of water 4.2 x 10\(^3\) J kg\(^{-1}\) K\(^{-1}\)]

  • A. 4.80 kJ
  • B. 20.16 kJ
  • C. 40.32 kJ
  • D. 22.17 kJ

Correct Answer: C. 40.32 kJ

Explanation

Heat needed to change 60g (0.06kg) of ice at 0\(^o\)C to water at 0\(^o\)

= 0.06 x 3.36 x 10\(^5\)J

= 0.2016 x 10\(^5\) J

Heat required to raise the temp. of 60g (0.06kg) of water from 0\(^o\)C to 80\(^o\)C

= 0.06 x 4.2 x 10\(^3\) x (80.0)J

= 0.06 x 4.2 x 10\(^3\) x 80

= 20.16 x 10\(^3\)

= 0.2016 x 10\(^5\)

Total heat needed = (0.2016 + 0.2016) 10\(^5\)J

= 0.4032 x 10\(^5\) J

= 40.32KJ



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