Demonstrate an Understanding of Energy Changes and Rates of Reaction - Science Assignment Help

Assignment Task:

Task:

1. If forming new bonds releases energy, how can a reaction ever be endothermic?(1 mark)

metal A has a heat capacity of 0.450 J/go

C while metal B has a heat capacity of
1.250 J/go C. If both metals are supplied with 1000.0 J of energy, which one will heat up more? Explain by describing what specific heat capacity defines (i.e. more than “this number is bigger/smaller”). (2 marks)

3. When there is going to be a frost in Florida, farmers will spray their crops with water before the frost hits thereby preventing the fruit from freezing. Using concepts from this unit, explain why this helps to save the fruit. (1 mark)

Curriculum Expectation D2. investigate and analyse energy changes and rates of reaction in physical and chemical processes, and solve related problems;
1. 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)

2. 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)

3. 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)

4. 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)

5. 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 kJH2+ 1⁄2 O2→ H2 O ΔH = -76.0 kJ

6. 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)

7. 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 kJ0.250 mol OR 0.250 mol−2250.0 kJ1mol

Why can’t we simply say that the energy of the reaction is -2250.0 kJ? (1 marks)

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