Use the information below to answer the following problems. a) A 500 g iron kett

Question

Use the information below to answer the following problems. a) A 500 g iron kettle is filled with 270 g of liquid water, both at 15 degree C. When placed on a hot stove, the water will eventually boil. How much total heat (in kJ) is required to bring the iron kettle and the water to 100 degree C? b) What percentage of this total heat is required to heat only the iron kettle? c) If a copper kettle (same number of moles) was used instead of the iron kettle, would MORE, LESS, or the SAME amount of total heat be required to bring the kettle to boil?

Explanation / Answer

Solution:- (a) mass of Iron kettle = 500g

mass of water filled in kettle = 270g

initial temperature = 15 0C

final temperature = 100 0C

change in temperature, delta T = 100 - 15 = 85 0C

Here the temperature is changing and no phase change is taking place so we use the equation, q = m c delta T

where, q is heat energy, m is mass, c is heat capacity and delta T is change in temperature.

we will calculate q for water and iron kettle separately and will add them up to get the total heat.

heat capacity for water si given in kJ/0C.mol so we will use moles of water in place of its grams.

qwater = 270 g x (1mol/18.02g) x 0.0753 kJ/0C.mol x 85 0C = 95.9 kJ

qIron = 500g x (1mol/55.845g) x 0.0290 kJ/0C.mol x 85 0C = 22.1 kJ

total heat = 95.9 kJ + 22.1 kJ = 118 kJ

(b) To calculate the percentage of heat required to heat only the iron kettle we will divide the q value of iron by the total heat and multiply by 100.

percent of heat required to heat iron = (22.1/118) x 100 = 18.7%

(c) From part b, moles of iron = 500g x 1mol/55.845g = 8.95 mol

so, moles of copper would also be 8.95.

heat capacity for copper is 0.0241 kJ/0C.mol.

let's calculate the q value for copper.

qcopper = 8.95 mol x 0.0241 kJ/0C.mol x 85 0C = 18.3 kJ

total heat = 95.9 kJ + 18.3 kJ = 114.2 kJ

So from calculations, Less amount of total heat is required to bring the kettle to boil when copper kettle is used instead of the Iron kettle.

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