rates of reactions ( year 12 )

Question 1

different ways of measuring rate of reaction ?

Answer 1

monitoring decrease in conc of reactant

. monitoring formation of product

for reactions that produce gases:

monitor volume of gas produced at regular time intervals using gas collections + monitor loss of mass of reactants using balance

.

Question 2

green box: monitoring the production of gas using gas collection

Answer 2

monitoring decomposition of hydrogen peroxide

1. hydrogen peroixde added to conical flask and bung replaced
2. initial vol of gas in measuring cylijnder recorded
3. manganese dioxide catalyst added to conical flask and bung replaced . start stop clock
4. vol of gas produced in measuring ctlinder recorded @ regular intervals until reaction complete
5. reaction complete when no more gas produced
6. plot graph for vol of gas produced over time

Question 3

green box : heterogenous catalysts and pollution

Answer 3

used in catalytic converters - reactants passed over platinum catalyst , harmful gases turned int oless harmful products

eg carbon monoxide turned into carbon dioxide in the catalytic converter, and nitrogen monoxide reduced to nitrogen gas , both are released into atmosphere, causing pollution

Question 4

practical for investigating the effect of temperature change on equillibruj m

Answer 4

cobalt chloride dissolved in water to produce pink solution

. reaction sensetive to change in temp

1. disolve coblat chloride in water in boiling tube. tehn add hcl. place tube in iced water. solution is pink colour
2. set up boiling water bath and transfer boiling tube into water. solution turns blue
3. put back i ncold water . soltuion turns back to pink
4. repeat as many times as you want, it shows the effect of temperature on equillibrium as forward reaction is endothermic thus when temperature increases, the eq shifts to the right in endothermic direction thus soslution turns blue. vice versa occurs too

( shifts in each direction MINIMISES increase in temperature!!!!!!)