In class, students were given the following problem: "Aluminum satellite dishes resist corrosion because aluminum reacts with ox
ygen gas to form a coating of aluminum oxide (Al2O3). What is the mass of Al2O3?"
a) Sally solved the problem by first finding the molar mass of aluminum oxide. She calculated the molar mass of Al2O3 as 43.0 g/mol. This is not the correct molar mass however. What did sally do wrong?
b) After finding the molar mass of Al2O3, Jacob set up the following conversion. (I'll add a pic)
Is this the correct set up for the problem?
a) Sally solved the problem by first finding the molar mass of aluminum oxide. She calculated the molar mass of Al2O3 as 43.0 g/mol. This is not the correct molar mass however. What did sally do wrong?
b) After finding the molar mass of Al2O3, Jacob set up the following conversion. (I'll add a pic)
Is this the correct set up for the problem?
1 answer:
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Given that, an experiment to measure the enthalpy change for the reaction of aqueous copper(II) sulfate, CuSO4(aq) and zinc, Zn(s) was carried out in a coffee cup calorimeter; the heat of the reaction in the whole system is calculated to be 2218.34 kJ
Heat of reaction (i.e enthalpy of reaction) is the quantity of heat that is required to be added or removed when a chemical reaction is taken place in order to maintain all of the compounds present at the same temperature.
The formula used to calculate the heat of the reaction can be expressed as follows:
Q = mcΔT
where:
- Q = quantity of heat transfer
- m = mass
- c = specific heat of water = 4.18 kJ/g °C (constant)
- ΔT = change in temparature
From the information given:
- The initial temperature (T₁) = 25° C
- The final temperature (T₂) = 91.5° C
∴
The change in temperature i.e. ΔT = T₂ - T₁
ΔT = 91.5° C - 25° C
ΔT = 66.5° C
The number of moles of CuSO₄ = 1.00 mol/dm³ × 50.0 cm³
= 0.05 moles
- Since the molar mass of CuSO₄ = 159.609 g/mol
Then;
Using the relation:
By crossing multiplying;
mass of CuSO₄ = number of moles of CuSO₄ × molar mass of CuSO₄
mass of CuSO₄ = 0.05 moles × 159.609 g/moles
mass of CuSO₄ = 7.9805 grams
∴
Using the formula from above:
Q = mcΔT
Q = 7.9805 g × 4.18 kJ/g °C × 66.5° C
Q = 2218.34 kJ
Therefore, we can conclude that the heat of the reaction is 2218.34 kJ
Learn more about the chemical reaction here: