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Chemistry > C2.4 > Flashcards

C2.4 Flashcards

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1
Q

What is a catalyst?

A

A substance that increases the rate of a chemical reaction without being altered or used up

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2
Q

What are the factors that affect the rate of a reaction?

A 
~ Temperature
~ Concentration of solutions
~ Pressure of gases
~ Surface area of solids
~ Use of a catalyst
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3
Q

What is the activation energy?

A

The minimum amount of energy required to cause a reaction

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4
Q

What are the particles like in a low temperature mixture?

A

~ Move slow

~ Less collisions as they have less energy so less particles can collide successfully

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5
Q

What are the particles like in a high temperature mixture?

A

~ Move fast

~ More collisions as they have more energy so more particles can collide successfully

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6
Q

What causes chemical reactions?

A

Reacting particles colliding with each other with sufficient energy

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7
Q

What are the particles like in low concentrations?

A

~ Less of them in that volume
~ Spread out
~ Less collisions

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8
Q

What are the particles like in high concentrations?

A

~ More of them in that volume
~ Close together
~ More collisions

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9
Q

What unit are concentrations of solutions given in?

A

Mol/dm^3

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10
Q

What does a decrease in surface area of a solid mean?

A

~ Fewer particles so less successful collisions

~ Less collisions = slower reaction

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11
Q

What does an increase in surface area of a solid mean?

A

~ More particles so more successful collisions

~ More collisions = faster reaction

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12
Q

What do catalysts lower?

A

The activation energy

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13
Q

What’s one way that a catalyst lowers the activation energy?

A

By providing a surface for molecules to attach to, therefore increasing the chance of them colliding

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14
Q

What are some processes that involve catalysts?

A

~ Cracking hydrocarbons

~ The manufacture of ammonia

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15
Q

Why is increasing the rate of chemical reactions important in industry?

A

Because it helps to reduce costs

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16
Q

What does lowering the activation energy mean for the industry?

A

Reactions can happen at a lower temperature, which reduces costs

17
Q

How can the rate of a chemical reaction be found?

A

Time

18
Q

How could you measure the amount of product formed in a decomposition reaction?

A

~ Weighing the mixture before and after the reaction

~ Or using a gas syringe to measure the volume of gas produced

19
Q

What is the test for oxygen?

A

Inserting a glowing splint into a jar of collected gas which will relight in the presence of oxygen

20
Q

Why could one reaction be faster than another?

A 
It could have...
~ A greater surface area 
~ A higher temperature 
~ A higher concentration 
~ Used a catalyst
21
Q

How do measure the rate of reaction between acid and sodium thiosulphate?

A

By drawing a cross on paper, placing it under the glass and measuring the time it takes to disappear
(The solution goes from clear to cloudy)

22
Q

What happens when the reactants have been used up?

A

The volume of gas/mass of product collected will stay the same (a horizontal line on a graph)

23
Q

What does increasing the pressure do to the particles?

A

~ It reduces the space they have
~ Particles are closer together
~ More successful collisions

24
Q

What are some examples of a catalyst?

A

~ Manganese oxide
~ Iron
~ Platinum
~ Nickel

25
Q

What’s a problem with increasing the temperature or pressure to speed up a reaction?

A

Costs money

26
Q

Different catalysts are used…

A

…for different reactions

27
Q

What are advantages of using catalysts?

A 
~ Less energy used
~ Speeds up reactions
~ Reusable
~ Lower production cost
~ Only needed in small amounts
28
Q

What are disadvantages of using catalysts?

A

~ Can be toxic

~ Can be expensive

29
Q

Why do powders react faster than larger pieces of solid?

A

Because they have a larger surface area to volume relation

30
Q

What does a gas syringe measure?

A

The volume of gas produced

Chemistry (20 decks)

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