A sample of mercury absorbed 257 J of heat and its mass was .45 kg. If it's temperature increased by 4.09 K, what is its specific heat in J° / kg K?

2 Answers
Jan 18, 2017

The specific heat formula is:

c = Q/(m × ΔT)

Where:

c: specific heat, in J/(kg.K)

Q: heat required for the temperature change, in J

ΔT: temperature change, in K

m: mass of the object, in kg

For our equation, we are given everything in the right units, so all we need is to plug in the numbers.

c = Q/(m × ΔT)

c = (257)/(.45 xx 4.09)

c = 139.64 (J)/(kgxxK)

Jan 18, 2017

The specific heat of mercury to two significant figures is "140 J"/("kg"*"K").

Explanation:

Use the equation color(red)(Q=mcDeltat), where Q is energy gained or lost in Joules; m is mass, in this case kg; c is specific heat, in this case in "J"/("kg"*"K")"; and Deltat is change in temperature, in this case Kelvins.
Determine what variables are known, and unknown. Then solve the equation for the unknown variable.

Known
Q="257 K"
m="0.45 kg"
Deltat="4.09 K"

Unknown
c_"Hg"

Solution
Rearrange the equation to isolate c_"Hg". Substitute the known values into the equation and solve.

c_"Hg"=(Q)/(m*Deltat)=(257"J")/((0.45"kg")xx(4.09"K"))="140 J"/("kg"*"K") rounded to two signficant figures