Topic 7 Flashcards

1
Q

7.1
Devise an experiment to investigate the effect of concentration
on the rate of reaction

A

-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

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2
Q

7.1
Devise an experiment to investigate the effect of temperature on the rate of reaction [3 marks]

A

-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

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3
Q

7.1
Devise an experiment to investigate the effect of using small vs large marble chips on the rate of reaction

A

-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

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4
Q

7.1 7.3
State 4 ways the rate of reaction can be increased

A

-↑ temp
-↑ pressure
-↑ conc
-Catalyst

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5
Q

7.2
Suggest 4 methods of determining the rate of reaction

A

-Collection of gas w/ gas syringe
-Collection of gas over water
-Monitor change in mass of gas (gas mass change)
-Monitor colour change

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6
Q

7.2
What does the reaction between calcium carbonate and hydrochloric acid produce?

A

Calcium chloride + Water + Carbon dioxide

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7
Q

7.2
What does the reaction between magnesium and hydrochloric acid produce?

A

Magnesium chloride + Hydrogen gas

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8
Q

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

A

-↓
-CO₂ can escape

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9
Q

7.3
Why do most reactions slow down overtime

A

Reactants are used up

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10
Q

7.3
What is a successful collision?

A

Produces reaction

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11
Q

7.3
Suggest a way you could monitor the rate of reaction over time during a practical

A

Use gas syringe
(measures change in v)

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12
Q

7.4
Explain the effect of increasing temperature on the rate of reaction

A

-Gain KE -> faster
-↑ frequent, successful collisions
-r. reaction ↑

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13
Q

7.4
Explain the effect of increasing concentration on the rate of reaction

A

-↑ particles closer together in same given v
-↑ frequent successful collisions
-r. reaction ↑

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14
Q

7.4
Explain the effect of increasing pressure on the rate of reaction

A

-Less space -> closer together
-↑ frequent successful collisions
-r. reaction ↑

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15
Q

7.4
Explain the effect of increasing surface area on the rate of reaction

A

-↑ particles exposed to reactant
-↑ frequent successful collisions
-↑ r. reaction

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16
Q

7.5
State the equation used to calculate the rate of reaction

A

r. reaction = change in amount of reac or prod/time

(usually the gradient)

17
Q

7.6
Define the term catalyst

A

-Speeds up r. reaction
-W/o altering products
-Its m remains unchanged

18
Q

7.6
Why are catalysts useful in industry?

A

-↓activation E
-Allow reactions to occur at ↓ temp + pressure
-↓ E cost required to ↑ temp + pressure

19
Q

7.6
Platinum is a very expensive catalyst. Suggest why this does not matter

A

Not used up -> can be re-used

20
Q

7.7
Describe how catalysts increase the rate of reaction

A

-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)

21
Q

7.7
Explain why catalysts in catalytic converters in car exhausts are spread onto a honeycomb structure rather than used as large pieces

A

-↑ SA
-↑ successful frequent collisions
-↑ r. reaction

22
Q

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

A

-Catalyst heats up
-Reaction faster as particles have more KE so move faster

23
Q

7.8
What is an enzyme? What is one use they have?

A

-Biological catalyst
-Speeds up r. reaction

-Produce alcoholic drinks

24
Q

7.8
Compare biological and chemical catalysts

A

-Both lower activation E -> speed r. reaction

-Bio: Specific to certain reactions, denatured by heat/pH
-Chemical: More resistant to heat/pH

25
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
26
7.10 What is an exothermic reaction?
Heat E given out
27
7.11 What is an endothermic reaction?
Heat E taken in
28
7.12 What type of reaction (endo or exo) is a) making bonds b) breaking bonds
a) exo b) endo
29
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
30
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)
31
7.15 Define the term activation energy
**Min** amount of E required for reaction to occur
32
State the formula for calcium carbonate
CaCO₃