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Untitled.notebook
1
November 11, 2012
1. A 1.55 g of CH4O sample is burnt in a calorimeter. If the molar heat of combuson of CH4O is ‐725 kJ/mole, and assuming that the 2.00 L of water absorbed all of the heat of combuson, what temperature change did the water experience (c water = 4.184J/gC)? (3)
Untitled.notebook
2
November 11, 2012
1. In order to obtain calibraon data for a bomb calorimeter, three 2.50 g samples of methanol were burned. The average temperature change of 4.23°C was recorded. The molar heat of combuson of methanol is ‐726 kJ/mol. Calculate the heat capacity of the bomb calorimeter. (3)
Untitled.notebook
3
November 11, 2012
1. A student dropped 5.00 g of an unknown acid HX, into 75.0 ml of aqueous Lithium Hydroxide, LiOH(s),. The reacon mixture absorbed 525 J as it warmed. Assuming it had a specific heat capacity of
4.184 :a. what was the temperature change of the reacon mixture?
(Hint: what is the mass of the new soluon?) (3)b. What was the molar enthalpy of reacon for the acid,
assuming a molar mass of 36.46 g/mol. (3)
Untitled.notebook
4
November 11, 2012
1. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: (4)
N2H4(l) + CH4O(l) → CH2O(g) + N2(g) + 3H2 (g)ΔH = ?
2NH3(g) → N2H4(l) + H2(g) ΔH = 22.5 kJ
2NH3(g) → N2(g) + 3H 2(g) ΔH = 57.5 kJ
3CH2O(g) + 3H2(g) → 3CH 4O(l) ΔH = 243.6 kJ
Untitled.notebook
5
November 11, 2012
1. A 275 g aluminum can is filled with 100.0 mL of water and suspended over a peanut. Calculate the fuel value of peanuts if burning a peanut with a mass of 0.358 g caused the temperature of the water to rise +5.46°C. (Hint: the aluminum can
AND the water absorb heat) (4)
Untitled.notebook
6
November 11, 2012
1. A. Use enthalpies of formaon to calculate the molar enthalpy for the reacon below. (4)
2 NH3(g) + 2 CH4(g) + 3 O2(g) à 2 HCN(g) + 6 H2O(l)
Enthalpies of formaon:
NH3(g) = ‐46.19 kJ/mol CH4(g) = ‐74.86 kJ/mol HCN(g) = +130.5 kJ/mol H2O(l) = ‐285.9 kJ/mol
Untitled.notebook
7
November 11, 2012
b. Use bond energies to calculate the enthalpy value for the above reacon. (4)
N‐H (389 kJ/mol); C‐H (414 kJ/mol); O=O (494 kJ/mol) CN (879 kJ/mol); O‐H (463 kJ/mol)
c. Compare the values for the molar enthalpy in a and b. Account for any similaries and differences. (2)
2 NH3(g) + 2 CH4(g) + 3 O2(g) à 2 HCN(g) + 6 H2O(l)
Untitled.notebook
8
November 11, 2012
1. Using bond energies from the table below, determine the enthalpies of combuson. (6)
a. Cyclobutene,
b. Ethanoic Acid
Untitled.notebook
9
November 11, 2012
1. Using bond energies from the table below, determine the enthalpies of combuson. (6)
a. Cyclobutene,
b. Ethanoic Acid
Untitled.notebook
10
November 11, 2012
1. For the following reacon:
P(s) + 5/2 Cl2(g) à PCl5(s) ∆Hrxn = ‐910 KJ/mol
Determine the energy of the P‐Cl bond. Cl‐Cl = 240KJ/mol. (4)