# Question #02750

Apr 7, 2016

76.7g

#### Explanation:

$Q = m {C}_{w} \left(\Delta {T}_{w}\right)$

Rearrange formula to solve for m
$m = \frac{Q}{{C}_{w} \Delta T} = \frac{Q}{{C}_{w} \left({T}_{f} - {T}_{o}\right)}$

Substitute data
$m = \frac{5455 J}{4.184 \frac{J}{g o C} \left(42.0 C - 25.0 C\right)}$

$m = \frac{5455 J}{4.184 \left(17\right)} = 76.69272 g$

Original data has three significant figures, so answer can only have three significant figures,
$m = 76.7 g$