mView?assignmentProblemiD-87622801 « previous | 8 of 16 |next Part A 75.0 mL of

Question

mView?assignmentProblemiD-87622801 « previous | 8 of 16 |next Part A 75.0 mL of H2O is initially at room temperature (22.0°C). A chilled steel rod at 2.0° C is placed in the water. If the final temperature of the systerm Specific heat of water 4.18 J/gC Specific heat of steel 0.452 J/g C is 21.5 °C, what is the mass of the steel bar? Express your answer numerically, in grams, to one significant figure. Hints mass of the steel = 17.8 Give Up Incorrect; One attempt remaining; Try Again Part B The specific heat of water is 4.18 J/g.°C. Calculate the molar heat capacity of water.

Explanation / Answer

Ans. Note the following changes taking place to reach the thermal equilibrium (21.50C)-

I. Water loses some heat and its temperature reduces from 22.00C to 21.50C

II. Steel bar gains some heat and its temperature increases from 2.00C to 21.50C.

# Amount of heat changed (gained or lost) during attaining thermal equilibrium is given by-

            q = m s dT                            - equation 1

Where,

q = heat gained or lost

m = mass

s = specific heat

dT = Final temperature – Initial temperature

# While reaching thermal equilibrium, the total heat lost by water must be equal to the total amount of heat gained by water. Note that heat loss is indicated by –ve sign.

It’s assumed that the density of water is equal to 1.000 g/ mL. So, mass of water is 75.0 g.

Let the mass of steel bar be m.

So,

- q1 (water) = q2 (iron)

Or, - [ 75.0 g x 4.18 J g-10C-1 x (21.50C – 22.00C) =

[ m x 0.452 J g-10C-1 x (21.50C – 2.00C)

            Or, 156.75 J = 8.814m J g-1

            Or, m = 156.75 J / 8.814 J g-1 = 17.784 g

Hence, mass of steel bar = 17.8 g ; [There are 3 significant figure in 17.8]

To express the answer in two significant figure, the answer can be rounded off to 20. (there are 2 significant figures in 20).

The answer can be written further in on significant figure as 0.2 x 102

Therefore, mass of steel bar = 0.2 x 102 (one significant figure)

Related Questions

Navigate

• Browse (All)
• Browse M
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.