Everything Science Grade 12

3.6 CHAPTER 3. REACTION RATES

(a) Write a balanced chemical equation for thisreaction.

(b) The rate of the reaction is determined by measuring the volume of gas that

is produced in the firstminute of the reaction.How would the rate ofthe

reaction be affected if:

i. a lump of calcium carbonate of the same mass is used

ii. 40 cm^3 of 0.1 mol.dm−^3 hydrochloric acid is used

More practice video solutions or help at http://www.everythingscience.co.za

(1.) 01pz (2.) 01q0 (3.) 01q1 (4.) 01q2

3.6 Chemical equilibrium

Having looked at factors that affect the rate ofa reaction, we now need to ask some

important questions. Does a reaction always proceed in the same direction or can it

be reversible? In other words, is it always true that a reaction proceeds from reactants

to products, or is it possible that sometimes, the reaction will reverse and the products

will be changed back into the reactants? And does a reaction always run its full course

so that all the reactantsare used up, or can a reaction reach a point where reactants

are still present, but there does not seem to beany further change taking place in the

reaction? The followingdemonstration might help to explain this.

Activity: Liquid-gas phase equilibrium

Apparatus and materials:

2 beakers; water; bell jar

Method:

1. Half fill two beakerswith water and mark the level of the water in each
   case.


2. Cover one of the beakers with a bell jar.


3. Leave the beakers and, over the course of a day or two, observe howthe
   water level in the two beakers changes. What do you notice? Note: You
   could speed up this demonstration by placing thetwo beakers over a Bun-
   sen burner to heat the water. In this case, it may be easier to cover the
   second beaker with a glass cover.