Chemistry, 01.11.2019 02:31 katy3865

Calculate the amount of energy in kilojoules needed to change 459 g of water ice at −10 ∘c to steam at 125 ∘c. the following constants may be useful: cm (ice)=36.57 j/(mol⋅∘c) cm (water)=75.40 j/(mol⋅∘c) cm (steam)=36.04 j/(mol⋅∘c) δhfus=+6.01 kj/mol δhvap=+40.67 kj/mol express your answer with the appropriate units. view available hint(s)

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Answer from: kaytek1

$1.41\times 10^3kJ$

Explanation:-

The conversions involved in this process are :

$(1):H_2O(s)(-10^0C)\rightarrow H_2O(s)(0^0C)\\\\(2):H_2O(s)(0^0C)\rightarrow H_2O(l)(0^0C)\\\\(3):H_2O(l)(0^0C)\rightarrow H_2O(l)(100^0C)\\\\(4):H_2O(l)(100^0C)\rightarrow H_2O(g)(100^0C)\\\\(5):H_2O(g)(100^0C)\rightarrow H_2O(g)(125^0C)$

Now we have to calculate the enthalpy change:

$\Delta H=[n\times c_{ice}\times (T_{final}-T_{initial})]+n\times \Delta H_{fusion}+[n\times c_{water}\times (T_{final}-T_{initial})]+n\times \Delta H_{vap}+[n\times c_{steam}\times (T_{final}-T_{initial})]$

where,

$\Delta H$ = enthalpy change = ?

m = mass of water = 459 g

$c_{s}$ = specific heat of ice = 36.57J/mol^0C

$c_{l}$ = specific heat of water = 75.40J/mol^0C

$c_{g}$ = specific heat of steam = 36.04J/gmol^0C

n = number of moles of water = $\frac{\text{Mass of water}}{\text{Molar mass of water}}=\frac{459g}{18g/mole}=25.5mole$

$\Delta H_{fusion}$ = enthalpy change for fusion = 6.01 KJ/mole = 6010 J/mole

$\Delta H_{vap}$ = enthalpy change for vaporization = 40.67 KJ/mole = 40670 J/mole

Now put all the given values in the above expression, we get:

$\Delta H=[25.5mole\times 36.57J/mol^0C\times (0-(-10))^0C]+25.5mole\times 6010J/mole+[25.5mole\times 75.40J/mol^0C\times (100-0)^0C]+25.5mole\times 40670J/mole+[25.5mole\times 36.04J/gmol^0C\times (125-100)^0c]$

$\Delta H=1414910.85J=1.41\times 10^3kJ$

(1kJ = 1000 J)

Therefore, the enthalpy change is $1.41\times 10^3kJ$

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

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: