Answer
84.8485 g
Step-by-step explanation
Initial temperature, T₁ = 148 °C
Final temperature, T₂ = 20.4 °C
ΔT = T₂ - T₁
ΔT = 20.4 - 148
ΔT = -127.6 °C
Since heat is released, i.e heat loss, then Q = -324.8 calories
specific heat of the lead bar, c = 0.0300 cal/g°C
Using Q = mcΔT, we can find m as shown below
![\begin{gathered} -324.8=m*0.0300*(-127.6) \\ -324.8=-3.828m \\ \text{Divide both sides by -3.828} \\ -(324.8)/(-3.828)=-(3.828m)/(-3.828) \\ \Rightarrow m=84.8485\text{ g} \end{gathered}](https://img.qammunity.org/2023/formulas/chemistry/high-school/vx52dx3wdplu3ramqasphzdkaxfnpocsmu.png)
The mass of the bar is 84.8485 g