Rate of Reactions Introductory Questions

1.	Cyclopropane, C3H6, is used in the synthesis of organic compounds and as a fast-acting anesthetic. It undergoes rearrangement to form propene. If cyclopropane disappears at a rate of 0.25 mol/s, at what rate is propene being produced?

2.	Ammonia, NH3, reacts with oxygen to produce nitric oxide, NO, and water vapour.
4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g)
At a specific time in the reaction, ammonia is disappearing at rate of 0.068 mol/(L • s). What is the corresponding rate of production of water?

3.	Hydrogen bromide reacts with oxygen to produce bromine and water vapour.
4 HBr (g) + O2 (g) → 2 Br2 (g) + 2 H2O (g)
How does the rate of decomposition of HBr (in mol/(L • s) ) compare with the rate of formation of Br2 (also in mol/(L • s) )? Express your answer as an equation.

4.	Magnesium metal reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas.
Mg (s) + 2 HCl (aq) → MgCl2 (aq) + H2 (g)
5.	Over an interval of 1.00 s, the mass of Mg(s) changes by -0.011 g.
(a)	What is the corresponding rate of consumption of HCl (aq) (in mol/s)?
(b)	Calculate the corresponding rate of production of H2 (g) (in L/s) at 20°C and 101 kPa.

6.	For each reaction, suggest one or more techniques for monitoring the progress of the reaction. Explain your answers.
(a)	CH3CH2CH2CH2CH=CH2 (l) + Br2 (aq) → CH3CH2CH2CH2CHBrCH2Br (l)
Hint: Br2 is brownish-orange. The other compounds are colourless.
(b) H2O2 (aq) → H2O (l) + 1/2 O2 (g)  
(c) CaCO3 (s) + H2SO4 (aq) → CaSO4 (aq) + CO2 (g) + H2O (l)
(d) 5 Fe2+ (aq) + MnO4- (aq) + 8 H+ (aq) → Mn2+ (aq) + 5 Fe3+ (aq) + 4 H2O (l)
Hint: The permanganate ion, MnO4-, is purple. All the other species in the reaction are colourless.
(e) N2 (g) + 3 H2 (g) → 2 NH3 (g)

7.	Identify five different factors that are likely to affect the rate of a reaction. Give a practical example of each.

8.	Which of the five factors that affect the rate of reactions applies only to heterogeneous systems? Give an example of such a system.

9.	What would happen to the rate of a reaction if the temperature were raised from 20°C to 40°C? Explain qualitatively and make a quantitative prediction.

10.	A match can be applied to a lump of coal with little effect. However, the ignition of coal dust has caused many fatal mining explosions. Explain.

11.	Signs warn about the dangers of having sparks or open flames near oxygen tanks or near flammable fuels. Which of the five factors that affect reaction rate are involved in each of these warnings?

12.	Enzymes in your body are generally present in extremely small quantities, but any substances that affect your enzymes are almost always very toxic and dangerous. Explain why this should be so, referring to reaction rates in your explanation.