C8- Rates and equilibrium Flashcards

1
Q

4 ways to monitor progress of a reaction

A

-Volume of gas produced
-Mass lost due to gas being formed
-Changes in colour or opacity
-Time for solid to disappear

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2
Q

How to calculate the rate of reaction at a specific time on a graph

A

-Draw a tangent to the curve at specific time
-Draw a right-angled triangle
-Calculate gradient by change in y / change in x
-Include units

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3
Q

Steeper gradient, reaction is…?

A

Steeper the gradient, faster the rate of reaction

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4
Q

3 types of practicals to calculate rate of reaction

A

Measure decreasing mass
Measure increasing volume of gas
Measure decreasing light passing through

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5
Q

Two equations for rate of reaction

A

Amount of reactant used / time
Amount of product made / time

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6
Q

Describe rate of reaction graph

A

-Fastest rate at beginning, maximum number of moles (0s)
-Rate decreases over time as reactants are used up
-Rate reaches 0 when one reactant is used up

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7
Q

5 factors that affect rate of chemical reactions

A

-Temperature
-Surface area of solids
-Concentration of solutions
-Pressure of gases
-Including catalyst

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8
Q

Collision theory

A

For a reaction to occur, reactant particles must collide with sufficient energy

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9
Q

Activation energy

A

Minimum energy that particles must have before they can react

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10
Q

3 general ways to increase rate of reaction

A

-Increase frequency of collisions
-Increase energy of collisions
-Reduce energy required for a reaction

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11
Q

What category does a higher SA:volume ratio increase?

A

Increases frequency of collisions

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12
Q

How to investigate the surface area affecting rate of reaction by volume of gas produced?

A

Measure 20cm3 of 1mol/dm3 HCl into beaker, add carbonate chips. Quickly place a bung connected to gas syringe, start timer. Wait 30s, record volume of gas. Repeat w powder. Higher vol of gas, faster rate of reaction.

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13
Q

Why does increasing SA:Volume ratio increase rate of reaction?

A

-Increases proportion of particles on surface
-Higher frequency of successful collisions
-Increase rate of reaction

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14
Q

What has the greatest effect on the rate of reaction: Increased frequency of collisions or increased energy of collisions?

A

An increased proportion of particles exceeding the activation energy

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15
Q

Why does an increased temperature increase rate of reaction?

A

-Particles have more KE
-Move faster, more frequent collisions
-Larger proportion of particles have the activation energy
-Greater frequency of successful collisions

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16
Q

What does a higher concentration of reactants increase? and why?

A

More particles moving around in the same volume, increase frequency of collisions.

17
Q

What does a higher pressure increase? and why?

A

Same number of particles in smaller volume, closer together.
Increase frequency of collisions

18
Q

Catalyst

A

Chemical substance that increases rate of reaction without being used up

19
Q

How does a catalyst increase rate of reaction?

A

Provide an alternative reaction pathway, with a lower activation energy

20
Q

2 key advantages of catalysts

A

-Save money, no paying to provide high energy
-Help environment, burning less fossil fuels

21
Q

Reversible reaction
and key symbol?

A

Where the products can react together to make the original reactants again
Two half arrows

22
Q

Reversible reaction observations with ammonium chloride

A

When heated ammonium chloride forms ammonia gas and hydrogen chloride, they then cool at top of tube before reacting with each other again to form ammonium chloride solids at the top

23
Q

How to investigate the effect of concentration on the rate of reaction

A

Measure 20cm3 of thiosulfate with a concentration of 8mol/dm3. Place thiosulfate in conical flask on top of a cross. Add 5cm3 HCl to conical flask, swirl once, start stopclock. When cross no longer visible, stop stopclock. Record time taken, calculate rate by using 1/time for reaction. Repeat with dif concs. Plot time against conc on a graph

24
Q

In reversible reactions what type of reaction are they?
Therefore the energy transferred each way?

A

One is endothermic and the other is exothermic
Amount of energy transferred to surroundings is the same amount taken back in

25
What happens when blue copper sulfate crystals are heated?
Copper sulfate contains water, when heated, the water evaporates to produce white anhydrous copper sulfate
26
How to show the heating of copper sulfate is reversible?
Heat copper sulfate, collect condensed vapour Stop heating when solid is white Add water to white solid Observe colour change back to blue
27
What is an equilibrium rate of reaction?
The rate of forward reaction equals the rate of reverse reaction
28
3 conditions for a dynamic equilibrium
Closed system Rate of forward reaction=rate of reverse reaction Moles/amount of each reactant and product remain constant
29
Le Chatelier Principle
When a change acts on a system at dynamic equilibrium, the position of equilibrium shifts to minimise the change
30
How can pressure affect gases at dynamic equilibrium? If they have equal moles on each side?
Increase in pressure, equilibrium shifts in favour of the side with fewer moles Equilibrium won't shift
31
How can temperature affect the dynamic equilibrium?
Increased temperature, equilibrium shifts in favour of endothermic side
32
How can the amount of substances affect the dynamic equilibrium?
Increased reactants or decreased products--> equilibrium shift to right
33
How can a catalyst affect the dynamic equilibrium?
Offers alternative reaction pathway, rates of reactions increase equally, equilibrium reached quicker but position not changed