Part A When 10.00 g of phosphorus is burned in O2( g ) to form P4O10( s ), enoug
ID: 559598 • Letter: P
Question
Part A
When 10.00 g of phosphorus is burned in O2(g) to form P4O10(s), enough heat is generated to raise the temperature of 2960 g of water from 18.0 C to 38.0 C.
Calculate the heat of formation of P4O10(s) under these conditions.
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Part B
Instant cold packs that are used to ice athletic injuries on the field contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves according to the following endothermic reaction:
NH4NO3(s)NH4+(aq)+NO3(aq)
To measure the enthalpy change for this reaction, 1.25 g of NH4NO3 is dissolved in enough water to make 25.0 mL of solution. The initial temperature is 25.8C and the final temperature (after the solid dissolves) is 21.9C.
Calculate the change in enthalpy for the reaction. (Use 1.0 g/mL as the density of the solution and 4.18 J/(gC) as the specific heat capacity.)
Express the enthalpy change in kilojoules per mole to two significant figures.
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Part C
What is the mass of the silver block?
Express your answer with the appropriate units.
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Part D
A silver block, initially at 68.1 C, is submerged into 100.0 g of water at 24.6 C in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 26.6 C.
What is the mass of the silver block?
Express your answer with the appropriate units.
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Part E
LP gas burns according to this exothermic reaction:
C3H8(g)+5O2(g)3CO2(g)+4H2O(g)Hrxn=2044kJ
What mass of LP gas is necessary to heat 1.6 L of water from room temperature (25.0 C) to boiling (100.0 C)? Assume that during heating, 16 % of the heat emitted by the LP gas combustion goes to heat the water. The rest is lost as heat to the surroundings.
Express your answer using two significant figures.
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Part F
A 2.51 g lead weight, initially at 10.6 C, is submerged in 7.86 g of water at 52.4 C in an insulated container.
What is the final temperature of both the weight and the water at thermal equilibrium?
Express the temperature in Celsius to three significant figures.
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(Both G and H)
Ethanol can be made from the fermentation of crops and is used as a fuel additive to gasoline.
Part G
Write a balanced equation for the combustion of ethanol (assume the water as a product of reaction to be gaseous).
Express your answer as a chemical equation. Identify all of the phases in your answer.
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Part H
Calculate Hrxn.
Express your answer using four significant figures.
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Hf = kJ/molExplanation / Answer
part A
P4(s) + 5O2(g) -----> P4O10(s)
no of mol of P4 = 10/124 = 0.0806 mol
heat released(q) = m*s*DT
= 2960*4.184*(38-18)
= 247692.8
= 247.693 kj
DH0f = - q/n = - 247.693/0.0806
= -3073.11 kj/mol
part B
NH4NO3(s)NH4+(aq)+NO3(aq)
heat absorbed(q) = m*s*DT
= 25*4.184*(25.8-21.9)
= 0.408 kj
no of mol of NH4NO3 = W/MWT = 1.25/80 = 0.0156 mol
DH0rxn = +q/n
= +0.408/0.0156
= +26.154 Kj/mol
part C
heat lost by silver block = heat gained by water
mass of silver*s*DT = mass of water*s*DT
m*0.233*(68.1-26.6) = 100*4.184*(26.6-24.6)
m = mass of silver = 86.54 g