3 A solution is prepared by dissolving 3.50 grams of NH4Cl in enough water to make 500 mL of solution. What is the concentration of this solution?
A) 0.0327 M
B) 0.0654 M
C) 0.131 M
D) 0.262 M
7 For the reaction N2O4(g) 2NO2(g) what is the effect of removing NO2 from the reaction vessel?
A) what happens depends on the temperature
B) the reaction will shift left to right
C) there will be no further reaction
D) the reaction will shift right to left
11 In an energy diagram for an exothermic chemical reaction which of the following is true?
A) the energy of the products is lower than that of the reactants
B) the energy of the transition state is higher than that of the reactants
C) both (a) and (b) are true
D) both (a) and (b) are false
12 What is the effect of increasing the temperature at which a reaction is carried out?
A) in all cases the rate of reaction decreases
B) in virtually all cases the rate of reaction decreases
C) in all cases the rate of reaction increases
D) in virtually all cases the rate of reaction increases
13. A particular chemical reaction carried out at 20oC takes 2 hours. How long will it take to carry out the reaction at 40oC?
A) 0.5 hour
B) 1 hour
C) 4 hours
D) 8 hours
14. For the reversible exothermic reaction 3H2(g) + N2(g) 2NH3(g) what is the effect of adding heat to the reaction vessel?
A) the reaction will shift right to left
B) there will be no further reaction
C) what happens depends on the temperature
D) the reaction will shift left to right
15. For the exothermic reaction 3H2(g) + N2(g) 2NH3(g) what is the effect of removing NH3 from the reaction vessel?
A) the reaction will shift left to right
B) the reaction will shift right to left
C) there will be no further reaction
D) what happens depends on the temperature
化學問題 +20 急!
2009-06-09 10:51 pm
回答 (1)
2009-06-10 4:43 am
✔ 最佳答案
3. C
Molar mass of NH4Cl = 14 + 1x4 + 35.5 = 53.5 g/mol
No. of moles of NH4Cl = 3.5/53.5 = 0.0654 mol
Volume of the solution = 500/1000 = 0.5 L
Concentration of this solution = 0.0654/0.5 = 0.131 M
7. B
According to Le Chatelier's principle, the equilibrium positive will shift to the right, in order to increase the concentration of NO2.
11. C
A is true. The reactants with higher energy are changed to the products with lower energy. The excess energy is released so that the reaction is exothermic.
B is also true. In any reaction, the transition state must have a higher energy than the products and the reactants.
12. C
In higher temperature, more reactant species have energy higher than the activation energy. Therefore, more reactant species would react in a certain period of time.
13. A
For most reactions, when temperature is increased by 10oC, the reaction rate would be approximately doubled.
14. A
According to Le Chatelier's principle, the equilibrium position will shift to the right because the backward reaction is endothermic.
15. A
According to Le Chatelier's principle, the equilibrium position will shift to the right in order to increase the concentration of NH3
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