Question

Show your work with good use of units, rounding, and significant figures. [Hint: it is good practice to show the value of your answer before you round off to the final answer with the correct significant figures!]
(8 points) How much heat is required to convert 10.00 g of ice at –20.00°C to water at 25°C. The specific heat of ice is 2.09J/g°C; the specific heat of water is 4.182 J/g°C; the heat of fusion is 333.0 J/g.

Group of answer choices

Answer 1

Heat required : 4.8 kJ

Further explanation

The heat to change the phase can be formulated :

Q = mLf (melting/freezing)

Q = mLv (vaporization/condensation)

Lf=latent heat of fusion

Lv=latent heat of vaporization

The heat needed to raise the temperature

Q = m . c . Δt

1. heat to raise temperature from -20 °C to 0 °C

$\tt Q=10\times 2.09\times (0-(-20)=418~J$

2. phase change(ice to water)

$\tt Q=10\times 333=3330~J$

3. heat to raise temperature from 0 °C to 25 °C

$\tt Q=10\times 4.18\times (25-0)=1045~J$

$\tt Q~tot=418+3330+1045=4793~J\rightarrow rounding~and~2~sig~figs=4.8~kJ$