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Chemistry > Rates > Flashcards

Rates Flashcards

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1
Q

A chemical reaction only happens when…

A

the reactant particles collide with enough energy

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2
Q

The amount of energy the particles need to react is called?

A

Activation Energy

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3
Q

What is collision frequency?

A

How often the particles collide with each other

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4
Q

What is percentage success?

A

The percentage of collisions that have enough energy

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5
Q

What 2 factors affect the collision frequency of rate?

A

Solid surface area
Solution concentration

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6
Q

What to factors affect the percentage success of rate?

A

Temperature
Catylists

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7
Q

What is the equation for rate?

A

Rate = collision frequency x percentage success

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8
Q

How does increasing the concentration/pressure increase rate?

A

There are more particles per unit volume
So collision frequency is higher
So there are more successful collisions per unit time

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9
Q

How do you increase concentration?

A

Dissolving more solute particles

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10
Q

How can you increase pressure?

A

Making the reaction vessel smaller

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11
Q

What experiment is used to demonstrate the effect of concentration?

A

Reacting thiosulphate solution with hydrochloric acid

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11
Q

How can you increase the surface area?

A

Cutting or grinding up the solid

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11
Q

What experiment is used to demonstrate the effect of surface area on rate?

A

Calcium carbonate chips with hydrochloric acid

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12
Q

Describe the relationship between rate and concentration

A

Rate is directly proportional to concentration
(straight line passing through graph)

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12
Q

How does increasing surface area increase rate?

A

More solid is exposed to the other particles
So collision frequency is higher
So there are more successful collisions per unit time

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13
Q

Relating to surface area and rate - what happens in a graph?

A

It is steep at the start however the amount of reactants hasn’t changed so its final area on the graph won’t be different to when the solid isn’t cut up.

14
Q

How does increasing temperature increase rate?

A

The particles have more kinetic energy
So the percentage of collisions with enough energy is higher
So there are more successful collisions per unit time

15
Q

What experiment is used to demonstrate the effect of temperature?

A

Reacting magnesium with hydrochloric acid (BY HEATING)

16
Q

Describe the relationship of temperature and rate on a graph?

A

Its not a straight line because rate isn’t proportional to temperature
It doesn’t go through origin because rate isn’t 0 at 0 degrees

17
Q

What are catalysts?

A

Substances which increase rate and remain chemically unchanged

18
Q

How do catalysts increase rate?

A

They provide an alternative route with a lower activation energy
So the percentage of collisions with enough energy is higher
So there are more successful collision per unit time

19
Q

What experiment is used to demonstrate the effect of catalysts?

A

The decomposition of hydrogen peroxide which is catalysed by manganese oxide (black solid)

20
Q

Describe the relationship of catalysts and rate on graphs

A

More effective catalysts increase rate more effectively = steeper line through graph

21
Q

Why would all lines eventually flatten out in the same total volume, on a catalyst rate graph?

A

The initial amounts of reactants would stay the same

22
Q

If a compound isn’t a catalyst it…

A

doesn’t increase the rate of reaction
doesn’t lower activations energy by offering an alternative reaction pathway

23
Q

Na2S2O3(aq) + 2HCl(aq) →

(Sodium thiosulphate + Hydrochloric acid)

A

2NaCl(aq) + S(s) + SO2(g) + H2O(l)

24
Q

CaCO3(s) + 2HCl(aq) →

(Calcium carbonate + Hydrochloric acid)

A

CaCl2(aq) + H2O(l) + CO2(g)

25
Q

Mg(s) + 2HCl(aq) →

(Magnesium + Hydrochloric acid)

A

MgCl2(aq) + H2(g)

26
Q

2H2O2(aq) →

(Hydrogen peroxide)

A

2H2O(l) + O2(g

27
Q

Definition of rate

A

The change in concentration of a reactant or product per unit time.

28
Q

Definition of rate of reaction

A

a process in which one or more substances, (the reactants) are converted to one or more different substances, (the products)

29
Q

What slows down reactions?

A

Add water to neutralise acids
Cooling reaction

Chemistry (8 decks)

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