Question

A sample of solid magnesium is heated with an electrical coil. If 165 Joules of energy are added to a 14.5 gram sample initially at 24.3°C, what is the final temperature of the magnesium?

A sample of liquid water is heated with an electrical coil. If 1.04×10³ Joules of energy are added to a 13.2 gram sample initially at 20.7°C, what is the final temperature of the water?

Answer 1

Answer – We are given, heat, q = 165 J, mass of Mg = 14.5 g , ti = 24.3^oC , tf = ?

We know the specific heat for Mg = 1.020 J/g^oC

We know the heat formula

Heat, q = m*C*Δt

    165 J = 14.5 g * 1.020 J/g^oC *(tf-24.3^oC)

165 J = 14.79 tf – 359.4

165+359.4 = 14.79 tf

So, 14.79 tf = 524.4

So, tf = 524.4 / 14.79

           = 35.45^oC

The final temperature of the magnesium is 35.45^oC.

Second question – We are given, heat, q = 1.04*10³ J, mass of Mg = 13.2 g , ti = 20.7^oC , tf = ?

We know the specific heat for water = 4.184J/g^oC

We know the heat formula

Heat, q = m*C*Δt

    1.04*10³ J = 13.2 g * 4.184 J/g^oC *(tf-20.7^oC)

1.04*10³ J = 55.23 tf – 1143.2

1.04*10³ J + 1143.2 = 55.23 tf

So, 55.23 tf = 2183.2

So, tf = 2183.2 / 55.23

           = 39.5^oC

The final temperature of the water is 39.5^oC.