Everything Science Grade 12

3.2 CHAPTER 3. REACTION RATES

(a) Complete the table by calculating the rate ofeach reaction.

(b) Which is the fastest reaction?

(c) Which is the slowest reaction?

2. Two reactions occursimultaneously in separate reaction vessels. The reactions
   are as follows:

Mg + Cl 2 → MgCl 2

2Na + Cl 2 → 2NaCl

After 1 minute, 2 g of MgCl 2 have been produced inthe first reaction.

(a) How many moles ofMgCl 2 are produced after 1 minute?

(b) Calculate the rate of the reaction, using theamount of product thatis pro-

duced.

(c) Assuming that the second reaction also proceeds at the same rate,calcu-

late...

i. the number of molesof NaCl produced after1 minute.

ii. the mass (in g) of sodium that is needed for this reaction to take place.

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3.2 Factors affecting reaction rates

ESCAR

Several factors affect the rate of a reaction. Itis important to know these factors so

that reaction rates can be controlled. This is particularly important when it comes to

industrial reactions, so that productivity can bemaximised. The following are some of

the factors that affect therate of a reaction.

1. Nature of reactants
   Substances have different chemical properties and therefore react differently and
   at different rates.


2. Concentration (or pressure in the case of gases)
   As the concentration ofthe reactants increases,so does the reaction rate.


3. Temperature
   If the temperature of thereaction increases, so does the rate of the reaction.