What is meant by thermal equilibrium?
Two bodies have the same kinetic energy but their temperature is different.
Two bodies have different kinetic energy so their temperature is different.
Two bodies have the same kinetic energy so their temperature is the same.
Two bodies have different kinetic energy but their temperature is the same.
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Which of the following best explains why the reactions represented in the table are exothermic?
Balanced equation for the combustion of one mole of the compound | ΔHoc (kJ/mol ) |
|---|---|
C2H6 (g)+ 3.5 O2 (g) → 2CO2 (g) + 3H2O (l) | -1560 |
C3H8 (g)+ 4.5 O2 (g) → 3CO2 (g) + 4H2O (l) | -2020 |
The energy released in forming the bonds in the products is less than the energy required to break the bonds in the reactants.
The energy released in forming the bonds in the products is more than the energy required to break the bonds in the reactants.
The number of bonds in the product molecules is less than the number of bonds in the reactant molecules.
The number of bonds in the product molecules is more than the number of bonds in the reactant molecules.
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Which statement about energy diagrams is correct?
An energy diagram for an exothermic reaction has the reactants at higher energy than the products with a positive enthalpy change.
An energy diagram for an endothermic reaction has the reactants at lower energy than the products with a positive enthalpy change.
An energy diagram for an exothermic reaction has the reactants at lower energy than the products with a negative enthalpy change.
An energy diagram for an endothermic reaction has the reactants at lower energy than the products with a negative enthalpy change.
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A metal spoon is placed in a cup of hot coffee. Which statement best describes the heat transfer process?
Heat flows from the spoon to the coffee until they reach the same temperature.
Heat flows from the coffee to the spoon until they reach the same temperature.
The spoon heats up but does not affect the temperature of the coffee.
No heat transfer occurs because metals are good conductors.
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Which of the following statements are correct about the dissolution of an ionic compound?
I. The enthalpy of hydration is always an exothermic process
II. If the lattice energy is greater than the hydration energy, the dissolution process is endothermic
III. To calculate the enthalpy change of solution we use:
ΔHsolution = ΔHlattice - ΔHhydration
I only
I and II only
I and III only
I, II and III
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