Unit 5 (Chem) - Revision Quiz #4

The diagram represents which type of reaction

• endothermic
• exothermic

if less heat energy is released in making bonds in the products than is taken in when breaking bonds in the reactants

• Endothermic

• Exotermic

• Exothermic

• Entrothermic

Endothermic:_________:__________

Exothermic:_________:__________

• positive:warm

  negative:cold

• positive:warm

  negative:warm

• positive:cold

  negative:cold

• positive:cold

  negative:warm

Define 'Enthalpy'

• a) Energy stored in the movement of molecules in a substance
• b) The opposite of temperature
• c) The temperature of a molecule
• d) Energy stored in the chemical bonds in a substance

Match the definition below to the correct term.

The enthalpy change that takes place when one mole of a compound is formed from its elements in their standard states under standard conditions.

• The enthalpy of neutralisation

• The enthalpy of combustion

• The enthalpy of formation

• The enthalpy of reaction

What does the circle mean in ΔH°?

• Standard Conditions (T=298.15 K P=1 atm)

• Standard Temperature and Pressure (T=273.15 K P=1 atm)

• Degree K

• Degree C

Define standard enthalpy of combustion.

• Heat released when one mole of substance is burnt completely in excess oxygen.

• Heat absorbed when one mole of substance is burnt completely in excess oxygen under standard state.

• Heat released when one mole of substance is burnt completely in excess oxygen under standard state.

• Heat change when one mole of substance is burnt partially in excess oxygen under standard state.

Which of the equation below refers to the standard enthalpy of formation, ΔH_f^o?

• Na(g) ---> Na⁺(g) + e^- ΔH = -364 kJmol^-1

• C₂H₅OH(l) + 3O₂(g) ---> 2CO₂(g) + 3H₂O (l) ΔH = - 1286 kJmol^-1

• 2C(s) + 2H₂(g) ---> C₂H₄ (g) ΔH = - 52.3 kJmol^-1

• Na⁺(g) ---> Na⁺(aq) ΔH = - 364 kJmol^-1

Using the equation q = mcΔT, calculate the energy change (J) for the following reaction. 100g of water. Butane is burned underneath. Start temp = 298K; End temp = 318K

Assume c = 4.18J/K/g. Also give your answer a postive or negative sign.

Decide whether your answer should

Answer explanation

100 x 4.18 x 20 = 8360J

Negative sign because the reaction is exothermic

-8360J

How does a catalyst work in speeding up a reaction?

• By lowering the activation energy or reaction

• by giving them more energy

• by making them more available