Organic Chemistry Answers

The following chemical reaction is at equilibrium at 25°C in a 1.0 L flask, with [A] = 0.28 M.


A(g) mc028-1.jpg B(g) K = 2.47


Suppose that 0.10 moles of A is added to the system. What will be the concentration of B after equilibrium has re-established

which compound will have the larger magnitude enthalpy of hydration

I have a saturated saline solution in water at a fixed temperature A. Can I dissolve yet another salt and thus increase the density of the solution and bring the temperature back to value A without any salt precipitating.

When determining the energy of a reaction where 0.250 mol of a substance with a ΔHcomb = -2250.0 kJ/mol reacts, we perform this calculation: −2250.0 kJ 1mol = x kJ 0.250 mol OR 0.250 mol −2250.0 kJ 1mol Why can’t we simply say that the energy of the reaction is -2250.0 kJ? (1 marks) ( )

A student is determining the enthalpy of solution for ammonium nitrate by adding ammonium nitrate to a calorimeter and measuring the temperature change. The accepted value is ΔHsol’n = 25.7 kJ/mol. A student, not paying attention, adds 1.5g of ammonium nitrate instead of 1.0g. When they perform their calculations, they use 1.0g as the mass. Will their calculation result in an answer that is higher than the accepted value or lower? Explain. (2 marks)

Calculate the enthalpy of the following reaction: (3 marks) 2Mg + O2 → 2MgO Given: Mg + 2HCl → MgCl2 + H2 ΔH = -21.0 kJ MgO + 2HCl → MgCl2 + H2 O ΔH = -33.5 kJ H2 + ½ O2 → H2 O ΔH = -76.0 kJ

If 3.65g of butane is burned underneath a cup holding 1.00 L of water at 21.0o C, what will the final temperature of the water be (ΔHcomb = -3325 kJ/mol)? (3 marks)

When 25.0 mL of 0.25 mol/L LiOH and 25.0 mL of 0.25 mol/L HCl are mixed together, the temperature warms 15.8o C. What is the molar enthalpy of neutralization for LiOH? (3 marks)

Instant hot packs work by crystallizing sodium acetate (NaCH3COO). The molar enthalpy of crystallization for sodium acetate is -56.7 kJ/mol. How many grams of sodium acetate are needed to warm 125.0 mL of water from 21.0o C to 35.4o C? (3 marks)

When 2.35g Mg(OH)2

is added to 250.0 mL of water, the temperature of the water

raises from 20.5o

C to 36.0o

C. Calculate the molar enthalpy of solution. (3 marks