Topic 7 Flashcards
7.1
Devise an experiment to investigate the effect of concentration
on the rate of reaction
-10cm³ sodium thiosulfate (w/ measuring cylinder) into conical flask
-10cm³ HCl to same cf
-Cf on black cross
-Record t taken (w/ stop clock) for ╳ to disappear
-Repeat w/ diff concs sodium thiosulfate
-Repeat whole experi & work out mean for each conc
7.1
Devise an experiment to investigate the effect of temperature on the rate of reaction [3 marks]
-Water bath to heat solution to desired temp
-Record (w/ stop clock) t for colour change to occur -> obscure cross
-Repeat w/ diff temps
-Ensure same v of solution used each t
7.1
Devise an experiment to investigate the effect of using small vs large marble chips on the rate of reaction
-Fixed v (measuring cylinder) HCl in conical flask
-Fixed m (balance) SMALL marble chips in flask
-Stopper flask w/ bung + delivery tube
-Delivery tube into trough filled w/ water
-Upturned measuring cylinder over tube
-H₂ gas trapped in cylinder
-Measure gas v every 30 secs
-Continue until no more H₂ produced
-Repeat w/ same mass LARGE marble chips
7.1 7.3
State 4 ways the rate of reaction can be increased
-↑ temp
-↑ pressure
-↑ conc
-Catalyst
7.2
Suggest 4 methods of determining the rate of reaction
-Collection of gas w/ gas syringe
-Collection of gas over water
-Monitor change in mass of gas (gas mass change)
-Monitor colour change
7.2
What does the reaction between calcium carbonate and hydrochloric acid produce?
Calcium chloride + Water + Carbon dioxide
7.2
What does the reaction between magnesium and hydrochloric acid produce?
Magnesium chloride + Hydrogen gas
7.2
The change in the mass of a gas is monitored by placing marble chips into a solution of hydrochloric acid. The top is sealed with cotton wool. Explain what would happen to the reading on the balance
-↓
-CO₂ can escape
7.3
Why do most reactions slow down overtime
Reactants are used up
7.3
What is a successful collision?
Produces reaction
7.3
Suggest a way you could monitor the rate of reaction over time during a practical
Use gas syringe
(measures change in v)
7.4
Explain the effect of increasing temperature on the rate of reaction
-Gain KE -> faster
-↑ frequent, successful collisions
-r. reaction ↑
7.4
Explain the effect of increasing concentration on the rate of reaction
-↑ particles closer together in same given v
-↑ frequent successful collisions
-r. reaction ↑
7.4
Explain the effect of increasing pressure on the rate of reaction
-Less space -> closer together
-↑ frequent successful collisions
-r. reaction ↑
7.4
Explain the effect of increasing surface area on the rate of reaction
-↑ particles exposed to reactant
-↑ frequent successful collisions
-↑ r. reaction
7.5
State the equation used to calculate the rate of reaction
r. reaction = change in amount of reac or prod/time
(usually the gradient)
7.6
Define the term catalyst
-Speeds up r. reaction
-W/o altering products
-Its m remains unchanged
7.6
Why are catalysts useful in industry?
-↓activation E
-Allow reactions to occur at ↓ temp + pressure
-↓ E cost required to ↑ temp + pressure
7.6
Platinum is a very expensive catalyst. Suggest why this does not matter
Not used up -> can be re-used
7.7
Describe how catalysts increase the rate of reaction
-Provide alternate pathway
-W/ lower activation E
(Note: doesn’t increase frequency of collisions. Increases frequency of successful collisions bc particles have greater activation E)
7.7
Explain why catalysts in catalytic converters in car exhausts are spread onto a honeycomb structure rather than used as large pieces
-↑ SA
-↑ successful frequent collisions
-↑ r. reaction
7.7
Explain why catalysts are more effective when the engine has been running for a short time rather than when the engine is first started
-Catalyst heats up
-Reaction faster as particles have more KE so move faster
7.8
What is an enzyme? What is one use they have?
-Biological catalyst
-Speeds up r. reaction
-Produce alcoholic drinks
7.8
Compare biological and chemical catalysts
-Both lower activation E -> speed r. reaction
-Bio: Specific to certain reactions, denatured by heat/pH
-Chemical: More resistant to heat/pH
7.9
a) Name 4 chemical reactions that experience a change in heat energy (energy transferred to or from the surroundings)
b) How can the heat change be measured?
a) -Salt dissolve in water
-Neutralisation
-Displacement
-Precipitation
b) Thermometer
7.10
What is an exothermic reaction?
Heat E given out
7.11
What is an endothermic reaction?
Heat E taken in
7.12
What type of reaction (endo or exo) is
a) making bonds
b) breaking bonds
a) exo
b) endo
7.13
When will the overall heat energy change for a reaction be exothermic? When will it be endothermic?
Exo
-↑ heat E released when forming bonds than breaking
Endo
-↑ heat E released when breaking bonds than forming
7.14
Calculate the energy change when hydrogen and chlorine react to form hydrogen chloride
H-H + Cl-Cl -> 2H-Cl
State whether the reaction is exothermic or endothermic
Bond energies:
H-H = 436 kJ mol-¹
Cl-Cl = 243 kJ mol-¹
H-Cl = 432 kJ mol-¹
H-H
1 × 436 = 436
Cl-Cl
1× 243 = 243
Total E in (bonds broken) = 679
2H-Cl
2 × 432 = 864
Total E out (bonds made) = 864
E change = E in - E out
= 679 - 864
= -185 kJ mol -¹
Exothermic (bc negative sign)
7.15
Define the term activation energy
Min amount of E required for reaction to occur
State the formula for calcium carbonate
CaCO₃
