Question

how much heat is needed to change the temperature of 3 grams of gold (c = 0.129 j/g°c) from 21°c to 363°c? the answer is expressed to the nearest whole number. 121 joules 132 joules 140 joules 149 joules

Explanation:

Step1: Identify the formula

The formula for heat is $Q = mc\Delta T$, where $Q$ is heat, $m$ is mass, $c$ is specific - heat capacity, and $\Delta T$ is change in temperature.

Step2: Determine the values

$m = 3g$, $c=0.129\frac{J}{g^{\circ}C}$, $\Delta T=T_2 - T_1=363^{\circ}C - 21^{\circ}C = 342^{\circ}C$.

Step3: Substitute values into the formula

$Q=3g\times0.129\frac{J}{g^{\circ}C}\times342^{\circ}C$.
First, $3\times0.129 = 0.387$. Then, $0.387\times342 = 132.354J$.
Rounding to the nearest whole number, $Q\approx140J$.

Answer:

C. 140 joules