Question

35.5 grams of an unknown substance is heated to 103.0 degrees Celsius and then placed into a calorimeter containing 100.0 grams of water at 24.0 degrees Celsius. If the final temperature reached in the calorimeter is 29.5 degrees Celsius, what is the specific heat of the unknown substance?

Answer 1

Answer:

Specific heat of the unknown substance is 0.881 J/gC

Explanation:

Given:

Mass of unknown substance, m(s) = 35.5 g

Initial temperature of the substance, T1 = 103 C

Mass of water, m(w) = 100 g

Initial temperature of water, T1 = 24 C

Final temperature of solution, T2 = 29.5 C

Formula:

Heat (q) absorbed or evolved by a substance is given as:

$q = mc\Delta T = mc(T_{2}-T_{1})----(1)$

where, m = mass of the substance

c = specific heat

ΔT = change in temperature

Calculation:

Heat lost by the unknown substance = heat gained by water

Based on equation (1) we have:

Heat lost by the unknown substance = -m(s)*c(s)*ΔT

= -35.5*c*(29.5-103) = 2609.25c

heat gained by water = -m(w)*c(w)*ΔT=100*4.18*(29.5-24) =2299

Therefore,

2609.25c = 2299

c = 0.881 J/g C

Answer 2

delta t for water = 29.5 - 24.0 = 5.5 C heat gained by water = 4.18 J/gC x 100.0 g x 5.5 C = 2300 J sp ht = J/m dt = 2300 J / (35.5 g x 73.5) = 0.89 J/gC