If the heat of combustion of newspaper (i.e.heat energy) is 1.97 x 10 4 J/g, wha

Question

If the heat of combustion of newspaper (i.e.heat energy) is 1.97 x 104 J/g, what is the final temperature that 500.0 mL of water will reach in a bomb calorimeter if 1.20 g of newspaper is combusted? The initial temperature of the water is 25.0 C. (Cp water 4.184 J/gC)

-11.30 C

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A 15.6 g sample of unknown metal, initially at 225C, heated 100g of water from 21.2 to 27.3C upon being submerged in the water. Determine the specific heat of the unknown metal given that the specific heat of water is 4.184 J/gC. (Enter a numerical value only - no units)

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Convert the heat of combustion of kerosene from Cal/g to J/g. The heat of combustion for Kerosene is 11.0 Cal/g

(Enter a numerical value only - no units)

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What are the oxidation numbers for the 5 atoms in the following elements?

Al3+, FeO and H2S

Format your answer A, B, C, D, E (e.g. 0,-1,+2,-3,+4) no spaces either before or after the commas

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Explanation / Answer

1)

now

heat obtained from burning newspaper = mass x heat of combustion of newspaper

heat obtained from burning newspaper = 1.2 x 1.97 x 10^4

heat obtained from burning newspaper = 23640 J

now

this heat is used to increase the temperature of water

now

mass = density x volume

we know that

density of water = 1 g/ml

so

mass of water = 500 x 1 = 500 g

now

heat = mass x specific heat x temp change

so

Q = m x s x dT

23640 = 500 x 4.184 x ( Tf - 25)

Tf - 25 = 11.3

Tf = 36.30

so

the final temperature of the water is 36.30 C

2)

we know that

heat = mass x specific heat x temp change

Q = m x s x dT

so

heat gained by water = 100 x 4.184 x ( 27.3 - 21.2)

heat gained by water = 2552.24 J

now

we know that

heat lost by hot body = heat gained by cold body

in this case

heat lost by metal = heat gained by water

so

heat lost by metal = 2552.24 J

now

heat lost by metal = m x s x dT

15.6 x s x ( 225-27.3) = 2552.24

s = 0.8275

so

the specific heat of the metal is 0.8275 J /g C

3)

we know that

1 Cal = 4.184 J

given

heat of combustion = 11 Cal / g

heat of combustion = 11 x 4.184 J / g

heat of combustion = 46.024 J/g

4)

Al+3 , the oxidation number of aluminium is +3

FeO , the oxidation number of Fe is +2 and Oxygen (O) is -2

H2S , the oxidation number of Hydrogen is +1 and Sulfur (S) is -2

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