Question

How much energy is needed to heat and melt 3.0 kg of copper initially at 83°C?

Be mindful of significant figure rules for both multiplication and addition.

450 kcal
430 kcal
280 kcal
130 kcal

Answer 1

430 kcal

Step-by-step explanation:

Answer 2

As we know that in order to melt the copper we need to take the temperature of copper to its melting point

So here heat required to raise the temperature of copper is given as

`Q = ms\Delta T`

We know that

melting temperature of copper = 1085 degree C

Specific heat capacity of copper = 385 J/kg C

now we have

`Q = 3(385)(1085 - 83)`

`Q = 1157310 J`

`Q = 1157.3 kJ`

now in order to melt the copper we know the heat required is

`Q = mL`

here we know that

L = 205 kJ/kg

now from above formula

`Q = 3(205) kJ`

`Q = 615 kJ`

now total heat required will be

`Q = 1157.3 kJ + 615 kJ`

`Q = 1772.3 kJ`

As we know that

`1 Cal = 4.18 kJ`

now we have

`Q = (1772.3)/(4.18) = 430 KCal`