Chemistry, 20.11.2019 06:31 mrmendrala

How much heat is lost when 575 grams molten iron at 1825 k becomes solid iron at 293 k? the melting point or iron is 1811 k.

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Answer from: austin856

146 kJ

Explanation:

There are two heat flows in this question.

Heat lost on cooling + heat lost on solidifying = 0

q₁ + q₂ = 0

mCΔT + nΔHsol = 0

Data:

m = 575 g

C = 0.449 J·K⁻¹g⁻¹

T_i = 1825 K

T_f = 1811 K

ΔHsol = -13.8 kJ·mol⁻¹

Calculations:

(a) Heat lost on cooling

ΔT = T_f - T_i = 1811 K - 1825 K = -14 K

q₁ = mCΔT = 575 g × 0.449 J·K⁻¹g⁻¹ × (-14 K) = -361 J = -3.61 kJ

(b) Heat lost on solidifying

$n = \text{575 g} \times \dfrac{\text{1 mol}}{\text{55.84 g}} = \text{10.30 mol}\\\\q_{2} = n\Delta_{\text{sol}}H = \text{10.30 mol} \times \dfrac{\text{-13.8 kJ}}{\text{1 mol}}= \text{-142.1 kJ}$

q = q₁ + q₂ = -3.61 kJ - 142.1 kJ = -146 kJ

The heat lost was 146 kJ.

Answer from: Quest

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.

Write 15 uses of a mercury barometer along with its characterestics

Answer from: Quest

Its strengthits conductivity of heat and electricity its shiny colourmalleable and ductility

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How much heat is lost when 575 grams molten iron at 1825 k becomes solid iron at 293 k? the melting...