Unit 2 AOS1 Flashcards
Which of the following statements correctly describes what must occur when reactant particles collide and react?
(A) Colliding particles must have and equal amount of kinetic energy.
(B) Colliding particles must have different amount of kinetic energy.
(C) Colliding particles must have kinetic energy equal to or greater than the average kinetic energy
(D) Colliding particles must have kinetic energy equal to or greater than the activation kinetic energy of the reaction.
Correct ans. (D).
Which of the following is the correct definition of the rate of reaction?
(
A) The time it takes for all of the reactant to be used up.
(B) How fast the reaction is going at the end of 1 minute.
(C) How much a reaction is bubbling.
(D) The change in concentration of reactants or products over time.
Correct ans. (D).
Which of the following is the correct unit for measuring the rate of a reaction?
(A) M/L
(B) M/s
(C) mol/L
(D) mol/s
Correct ans. (B).
What is the correct unit for measuring the rate of a reaction?
M/s OR Ms^-1
How to answer “ Which of the following combinations of reactants will produce the greatest reactant rate”?
-Look for the reactant with the highest M/Molarity
- Look for the reactant in powdered/crushed state.
The following changes are made to a reaction mixture. Which change will lead to a decrease in reaction rate?
(A) Smaller particles are used.
(B) The temperature is changed from 311K to 301K.
(C) A catalyst is added.
(D) The concentration of an aqueous reactant is changed from 0.1M To 0.5M.
Correct ans. (B).
A 5.00 g of copper was dissolved in a beaker containing 500 ml of 2.00 M nitric acid. The equation for the reaction that occurred is:
3Cu(s) + 8HNO3(aq) —–> 3Cu (NO3)2(aq)+ 2NO(g)+ 4H20(I)
The changing mass of the mixture was observed over a period of time and the graph below was obtained. ( X- axis is the times in seconds and the Y-axis is the mass of the mixture in grams.)
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A) Explain why the mass of the mixture initially decreases over time.
A gas NO is produced and escapes the beaker. The mass of lost oxygen will result in an overall decrease in the mass of the mixture.
A 5.00 g of copper was dissolved in a beaker containing 500 ml of 2.00 M nitric acid. The equation for the reaction that occurred is:
3Cu(s) + 8HNO3(aq) —–> 3Cu (NO3)2(aq)+ 2NO(g)+ 4H20(I)
The changing mass of the mixture was observed over a period of time and the graph below was obtained. ( X- axis is the times in seconds and the Y-axis is the mass of the mixture in grams.)
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B) Based on the information provided, determine which is the limiting reagent.
Copper is the limiting reagent.
A 5.00 g of copper was dissolved in a beaker containing 500 ml of 2.00 M nitric acid. The equation for the reaction that occurred is:
3Cu(s) + 8HNO3(aq) —–> 3Cu (NO3)2(aq)+ 2NO(g)+ 4H20(I)
The changing mass of the mixture was observed over a period of time and the graph below was obtained. ( X- axis is the times in seconds and the Y-axis is the mass of the mixture in grams.)
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C) Sketch the graph and add a curve to show what would be expected if 500 mL of 1.00M nitric acid was used instead. Label the curve and explain the difference in shape.
The curve will be half as steep due to the decreased HNO3 concentration, but it will level off at the same mass as Cu is still the limiting reagent.
A 5.00 g of copper was dissolved in a beaker containing 500 ml of 2.00 M nitric acid. The equation for the reaction that occurred is:
3Cu(s) + 8HNO3(aq) —–> 3Cu (NO3)2(aq)+ 2NO(g)+ 4H20(I)
The changing mass of the mixture was observed over a period of time and the graph below was obtained. ( X- axis is the times in seconds and the Y-axis is the mass of the mixture in grams.)
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D) Add a curve to show what would be expected if 5.00 g powdered copper was used instead. Label the curve and explain the difference in shape.
The curve will be steeper due to the Cu increased Surface area, but it will level off at the same place as the number of moles of Cu is unchanged.
Which of the following factors would NOT increase the rate of decomposition of Hydrogen peroxide?
2 H2 O2 (aq) ——————> 2 H20(I) + 02 (g)
(A) Increasing the pressure of oxygen gas.
(B) Increasing the concentration of hydrogen peroxide.
(C) Increasing the temperature of hydrogen peroxide.
(D) Adding a potassium iodide catalyst.
Correct ans. (A).
Explain how a decrease in the concentration of a reactant would affect the rate of reaction. 3 marks
A decrease in Collision frequency which would lead to
a decrease in the frequency of successful collisions between particles which would decrease the rate of reaction.
Explain how a decrease in the volume of a gaseous reactant would affect the rate of reaction. 3 marks
A increase in pressure which would lead to a increase in Collision frequency which would lead to a increase in the frequency of successful collisions between particles which would increase the rate of reaction.
What is the effect on the rate of reaction when a catalyst is added and the concentration is increased. 2 marks
The activation energy decreases and the collision frequency increases.
Identity the type of bonding between the carbon and hydrogen atoms present in methane, and explain why methane is a gas at 20 degrees celicus. (3 marks).
The bond present between carbon and hydrogen atoms within a methane molecule are covalent bonds. Methane is a very small molecule, with no dipole moment (it has only symmetrically arranged non-polar covalent bonds) and therefore the melting/boiling point are expected to be very low, as such it is a gas at room temperature.
Do substances made of simple molecules conduct electricity? (1 mark)
Not usually, however, there are exceptions.
Do molecules have an overall charge, like ions. Explain why/why not ( 1 mark)
No, because molecules are always neutral/have no charge.
Do simple molecules have low or high boiling points and provide and example . ( 1 mark)
Low boiling point. e.g. methane.
The alloy is harder than pure aluminum, explain why. ( 2 marks)
They are made up of atoms of different sizes, rather than being uniform. This means that the layers of atoms cannot slide over each other easily, making the whole alloy much stronger than any of the pure metals that the alloy contains in isolation.
Explain why ionic compounds cannot conduct electricity as a solid. ( 1 mark)
Ionic compounds cannot conduct electricity when solid, as their ions are held in fixed positions and cannot move.
How many carbon atoms are there in 6g of carbon. ( 1 mark)
3.01x10^23 carbon atoms.
How many oxygen atoms are there in 0.1 mol of potassium permanganate, KMO4. ( 2 marks)
3.61x10^23 oxygen atoms.
How many hydrogen atoms are there in 1.2 mol of glucose, C6H12O6. ( 2 mark)
1.743x10^25 hydrogen atoms.
State how a decrease in temperature would affect the yield of ammonia and rate of reaction (3 mark).
Low temperatures favour the production of ammonia. If we decrease the temperature at equilibrium, the exothermic, forward reaction is favoured to oppose the reduction temperature. A high yield of ammonia is produced. However, low temperatures have a very slow rate of reaction.
