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ENTHALPY

Total questions: 15

Worksheet time: 8mins

Name
Class
Date
1.

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.

a)

The enthalpy of neutralisation

b)

The enthalpy of combustion

c)

The enthalpy of formation

d)

The enthalpy of reaction

2.
Define 'Enthalpy'
a)
a) Energy stored in the movement of molecules in a substance
b)
b) The opposite of temperature
c)
c) The temperature of a molecule
d)
d) Energy stored in the chemical bonds in a substance
3.

What does the circle mean in ΔH°?

a)

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

b)

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

c)

Degree K

d)

Degree C

4.

How do you calculate Enthalpy of a reaction?

a)

ΔH = ΔHproducts - ΔHreactants

b)

ΔT = q / mC

c)

ΔG = ΔH -TΔS

d)

E = mc2

5.

Define standard enthalpy of combustion.

a)

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

b)

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

c)

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

d)

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

6.

Which of the equation below refers to the standard enthalpy of formation, ΔHfo?

a)

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

b)

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

c)

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

d)

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

7.

The potential energy diagram of a reaction is shown. Which statement below is correct relating to this reaction?

a)

#1 represents the enthalpy change for this exothermic reaction.

b)

#2 represents the enthalpy change for this endothermic reaction.

c)

#3 represents the enthalpy change for this endothermic reaction.

d)

#4 represents the enthalpy change for this exothermic reaction.

8.

Change in enthalpy is also called as _______.

a)

Systematic Reaction

b)

Balanced Reaction

c)

Energy of Reaction

d)

Heat of Reaction

9.
The SI unit of heat and energy is the __________.
a)
calorie
b)
heat
c)
joule
d)
watt
10.
A catalyst works by
a)
changing the order of the reaction
b)
increasing the temperature
c)
lowering the activation energy
d)
making the activated complex
11.

What do we mean by the term standard conditions

a)

1atm, 20C and 1moldm3

b)

1atm, 0K and 1moldm3

c)

10atm, 273K and 10mol/dm3

d)

100kPa, 298K and 1mol/dm3

12.

Define the term Exothermic by picking the correct statements

a)

Products have less energy than the reactants

b)

ΔH is negative

c)

ΔH is positive

d)

Energy is given out to the surroundings (temperature goes up).

e)

products have more energy than the reactants

13.

What does the circle mean in ΔH°?

a)

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

b)

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

c)

Degree K

d)

Degree C

14.

Which symbol represents Enthalpy change?

a)

ΔH

b)

ΔT

c)

ΔG

d)

ΔS

15.

HfinalH_{final}   > HinitialH_{initial}  means _____

a)

change of enthalpy is positive and system absorbs heat

b)

change of enthalpy is negative and system absorbs heat

c)

change of enthalpy is positive and system loses heat

d)

change of enthalpy is negative and system loses heat