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WorksheetsChapter 5 - Thermochemistry SL Review
Total questions: 20
Worksheet time: 11mins
What energy changes occur when chemical bonds are formed and broken?
Energy is absorbed when bonds are formed and when they are broken
Energy is released when bonds are formed and when they are broken
Energy is absorbed when bonds are formed and released when they are broken
Energy is released when bonds are formed and absorbed when they are broken
The temperature of a 2.0 g sample of aluminum increases from 25C to 30C. How many joules of heat energy were added? (Specific heat of aluminum = 0.90 J/gK)
0.36
2.3
9.0
11
Using the equations:
C(s) + O2(g) → CO2(g) ΔH = -390 kJ
Mn(s) + O2(g) → MnO2(s) ΔH = -520 kJ
what is ΔH for the reaction: MnO2(s) + C(s) → Mn(s) + CO2(g)?
910
130
-130
-910
What is ΔH for the reaction below in kJ?
CS2(g) + 3O2(g) → CO2(g) + 2SO2(g)
(ΔHf (kJ/mol): CS2(g) = 110, CO2(g) = -390, SO2(g) = 290)
-570
-790
-860
-1080
Which statements about exothermic reactions are correct?
I. They have negative ΔH values II. The products have a lower enthalpy than the reactants III. The products are more energetically stable than the reactants
I and II only
I and III only
II and III only
I, II, and III
A sample of a metal is heated. Which of the following are needed to calculate the heat absorbed by the sample?
I. the mass of the sample II. the density of the sample III. the specific heat capacity of the sample
I and II only
I and III only
II and III only
I, II, and III
The average bond enthalpies for O-O and O=O are 146 and 496 kJ/mol respectively. What is the enthalpy change, in kJ, for the reaction below?
H-O-O-H(g) → H-O-H(g) + ½O=O(g)
-102
+102
+350
+394
What is the energy change (in kJ) when the temperature of 20 g of water increases by 10C?
20 x 10 x 4.18
2 x 283 x 4.18
(20 x 10 x 4.18)/1000
(20 x 283 x 4.18)/1000
When the solids Ba(OH)2 and NH4SCN are mixed, a solution is produced and the temperature drops. Which statement about the energetics of this reaction is correct?
The reaction is endothermic and ΔH is negative
The reaction is endothermic and ΔH is positive
The reaction is exothermic and ΔH is negative
The reaction is exothermic and ΔH is positive
For which of the following is the sign of the enthalpy change different from the other three?
CaCO3(s) → CaO(s) + CO2(g)
Na(g) → Na+(g) + e-
CO2(s) → CO2(g)
2Cl(g) → Cl2(g)
Which statements are correct for an endothermic reaction?
I. the system absorbs heat II. the enthalpy change is positive III. the bond enthalpy total for the reactants is greater than for the products
I and II only
I and III only
II and III only
I, II, and III
The mass m (in g) of a substance of specific heat capacity c (J/gK) increases by 1C. What is the heat change in J?
mct
mc(t+273)
mct/1000
mc(t+273)/1000
The average bond enthalpy for the C-H bond is 412 kJ/mol. Which process has an enthalpy change closest to this value?
CH4(g) → C(s) + 2H2(g)
CH4(g) → C(g) + 2H2(g)
CH4(g) → C(s) + 4H(g)
CH4(g) → CH3(g) + H(g)
Which type of reaction is referred to in the definition of standard enthalpy change of formation?
the formation of a compound from its elements
the formation of a crystal from its ions
the formation of a molecule from its atoms
the formation of a compound from other compounds
The following equation shows the formation of magnesium oxide from magnesium metal. Which statement is correct for this reaction?
2Mg(s) + O2(g) → 2MgO(s) ΔH = -1204 kJ
1204 kJ of energy are released for every mole of magnesium reacted
602 kJ of energy are absorbed for every mole of magnesium oxide formed
602 kJ of energy are released for every mole of oxygen reacted
1204 kJ of energy are released for every two moles of magnesium oxide formed
A simple calorimeter was used to determine the enthalpy of combustion of ethanol. The experimental value obtained was -920 kJ/mol. The Data Booklet value is -1371 kJ/mol. Which of the following best explains the difference between the two values?
incomplete combustion of the fuel
heat loss to the surroundings
poor ventilation in the laboratory
inaccurate temperature measurements
Which statement about bond enthalpies is correct?
bond enthalpies have positive values for strong bonds and negative values for weak bonds
bond enthalpy values are greater for ionic bonds than for covalent bonds
bond breaking is endothermic and bond making is exothermic
the carbon-carbon bond enthalpy values are the same in ethane and ethene
Approximate values of the average bond enthalpies, in kJ/mol, of three substances are:
H-H = 430, F-F = 155, H-F = 565
What is the enthalpy change in kJ for this reaction: 2HF → H2 + F2
+545
+2
-20
-545
Which statement is correct about the reaction shown?
2SO2(g) + O2(g) → 2SO3(g) ΔH = -196 kJ
196 kJ of energy are released for every mole of SO2(g) reacted
196 kJ of energy are absorbed for every mole of SO2(g) reacted
98 kJ of energy are released for every mole of SO2(g) reacted
98 kJ of energy are absorbed for every mole of SO2(g) reacted
For the reaction 2H2(g) + O2(g) → 2H2O(g) the bond enthalpies (in kJ/mol) are
H-H = x, O=O = y, O-H = z
Which calculation will give the value, in kJ/mol, of ΔH for the reaction?
2x + y - 2z
4z - 2x - y
2x + y - 4z
2z - 2x - y
