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All questions of Chemical Energetics for Grade 9 Exam
Use the bond energies provided to calculate the amount of energy given out when propane is burnt.
C3H8 + 5O2 → 3CO2 + 4H2O- a)2054kJmol-1
- b)-628kJmol-1
- c)1958kJmol-1
- d)-2054kJmol-1
Correct answer is option 'D'. Can you explain this answer?
Use the bond energies provided to calculate the amount of energy given out when propane is burnt.
C3H8 + 5O2 → 3CO2 + 4H2O
C3H8 + 5O2 → 3CO2 + 4H2O
a)
2054kJmol-1
b)
-628kJmol-1
c)
1958kJmol-1
d)
-2054kJmol-1
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Elite Coaching Classes answered |
Remember that CO2 has 2 C=O double bonds not single bonds
Using the bond energies provided, calculate the energy change for this reaction.
2CH4 + O2 → 2CH3OH- a)-1471kJ/mol
- b)-329kJ/mol
- c)-89kJ/mol
- d)+2567kJ/mol
Correct answer is option 'B'. Can you explain this answer?
Using the bond energies provided, calculate the energy change for this reaction.
2CH4 + O2 → 2CH3OH
2CH4 + O2 → 2CH3OH
a)
-1471kJ/mol
b)
-329kJ/mol
c)
-89kJ/mol
d)
+2567kJ/mol
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Elite Coaching Classes answered |
When carrying out these calculations, always subtract the reactants energy from the products
In the Haber process, nitrogen and hydrogen are reacted together to produce ammonia. Use the bond energies provided to calculate the overall energy change in the reaction.
N2 + 3H2 ⇌ 2NH3- a)-93kJ
- b)-4599kJ
- c)1401kJ
- d)93kJ
Correct answer is option 'A'. Can you explain this answer?
In the Haber process, nitrogen and hydrogen are reacted together to produce ammonia. Use the bond energies provided to calculate the overall energy change in the reaction.
N2 + 3H2 ⇌ 2NH3
N2 + 3H2 ⇌ 2NH3
a)
-93kJ
b)
-4599kJ
c)
1401kJ
d)
93kJ
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Elite Coaching Classes answered |
945 + (3x436) - (6x-391) = -93kJ
What does the term 'enthalpy' represent in a chemical reaction?- a)Total heat content of a system
- b)Rate of reaction
- c)Amount of reactants used
- d)Temperature change during the reaction
Correct answer is option 'A'. Can you explain this answer?
What does the term 'enthalpy' represent in a chemical reaction?
a)
Total heat content of a system
b)
Rate of reaction
c)
Amount of reactants used
d)
Temperature change during the reaction
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Elite Coaching Classes answered |
Enthalpy is the total heat content of a system at constant pressure, including both the internal energy and the product of pressure and volume.
Pick the correct combination for the correct information regarding bond energies.- a)Bond breaking - Exothermic - Takes in energy
Bond making - Endothermic - Gives out energy - b)Bond breaking - Endothermic - Takes in energy
Bond making - Exothermic - Gives out energy - c)Bond breaking - Endothermic - Gives out energy
Bond making - Exothermic - Takes in energy - d)Bond breaking - Exothermic - Gives out energy
Bond making - Endothermic - Takes in energy
Correct answer is option 'B'. Can you explain this answer?
Pick the correct combination for the correct information regarding bond energies.
a)
Bond breaking - Exothermic - Takes in energy
Bond making - Endothermic - Gives out energy
Bond making - Endothermic - Gives out energy
b)
Bond breaking - Endothermic - Takes in energy
Bond making - Exothermic - Gives out energy
Bond making - Exothermic - Gives out energy
c)
Bond breaking - Endothermic - Gives out energy
Bond making - Exothermic - Takes in energy
Bond making - Exothermic - Takes in energy
d)
Bond breaking - Exothermic - Gives out energy
Bond making - Endothermic - Takes in energy
Bond making - Endothermic - Takes in energy
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Elite Coaching Classes answered |
Remember Exothermic Exit and Endothermic Enter
The overall energy change in a chemcial reaction is -24kJ/mol. What does this tell us about the reaction?- a) It is endothermic
- b) More energy was taken in than given out
- c) It is exothermic
- d) The temperature decreased
Correct answer is option 'C'. Can you explain this answer?
a)
It is endothermic
b)
More energy was taken in than given out
c)
It is exothermic
d)
The temperature decreased
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Elite Coaching Classes answered |
A negative energy change shows the reaction is exothermic and so heat and/or other energy has been transferred into the surroundings, often increasing the temperature
Which of the following statements describes an exothermic reaction?- a)It absorbs heat from the surroundings.
- b)It releases heat to the surroundings.
- c)It absorbs light energy.
- d)It increases the temperature of the surroundings.
Correct answer is option 'B'. Can you explain this answer?
Which of the following statements describes an exothermic reaction?
a)
It absorbs heat from the surroundings.
b)
It releases heat to the surroundings.
c)
It absorbs light energy.
d)
It increases the temperature of the surroundings.
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Elite Coaching Classes answered |
An exothermic reaction releases heat to the surroundings, making it feel warm.
Use the bond energies provided to calculate the energy change in the following reaction.
oxygen + hydrogen → water- a)1856kJ/mol
- b)1370kJ/mol
- c)442kJ/mol
- d)486kJ/mol
Correct answer is option 'D'. Can you explain this answer?
Use the bond energies provided to calculate the energy change in the following reaction.
oxygen + hydrogen → water
oxygen + hydrogen → water
a)
1856kJ/mol
b)
1370kJ/mol
c)
442kJ/mol
d)
486kJ/mol
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Elite Coaching Classes answered |
Add together the energy of each bond of the reactants, do the same for the bonds in the products. Then subtract the total bond energy of the reactants from that of the products to get the answer
Use the bond energies provided to calculate the energy change in the following reaction.
H2 + Cl2 → 2HCl- a)-247kJ/mol
- b)-1543kJ/mol
- c)-185kJ/mol
- d)-158kJ/mol
Correct answer is option 'C'. Can you explain this answer?
Use the bond energies provided to calculate the energy change in the following reaction.
H2 + Cl2 → 2HCl
H2 + Cl2 → 2HCl
a)
-247kJ/mol
b)
-1543kJ/mol
c)
-185kJ/mol
d)
-158kJ/mol
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Elite Coaching Classes answered |
Bond breaking = 436+243kJ/mol; bond making 2x432kJ/mol
What is the role of enzymes in biological reactions?- a)They act as reactants.
- b)They increase the temperature of the reaction.
- c)They speed up the reaction without being used up.
- d)They change the color of the reaction mixture.
Correct answer is option 'C'. Can you explain this answer?
What is the role of enzymes in biological reactions?
a)
They act as reactants.
b)
They increase the temperature of the reaction.
c)
They speed up the reaction without being used up.
d)
They change the color of the reaction mixture.
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Elite Coaching Classes answered |
Enzymes are biological catalysts that accelerate chemical reactions in living organisms without being consumed in the process.
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Chemistry for Grade 9
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