C8 Flashcards

1
Q

You can compare solids wth different surface areas quantitatively by looking at their _____

A

surface area to volume ratio

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2
Q

Why is reaction rate important in the chemical industry?

A

To make sure products are made quickly and cheaply

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3
Q

Why is it cheaper to use catalysts?

A

Because otherwise to get the same reaction it would require higher temperatures and/or pressures every time

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4
Q

Why is food cooled?

A

To slow unwanted chemical reactions

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5
Q

Why is chemical equilibrium described as dynamic?

A

Both forward and backward reactions still happen

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6
Q

Why does increasing the concentration of reactants in a solution increase the rate of reaction?

A

Because there are more particles of the reactants moving around in the same volume of solution.

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7
Q

When has a state of dynamic equilibrium been reached?

A

When the forward and reverse reactions are continously taking place

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8
Q

What types of metals are catalysts often?

A

Very expensive metals like gold, platinum and palldium

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9
Q

What piece of apparatures could be used to measure the volume of gas produced in a reaction?

A

A gas syringe

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10
Q

What is used to show that a reaction is reversible?

A

Two ‘half-arrows’

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11
Q

What is the rate of reaction?

A

How fast reactants turn into products

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12
Q

What is the method to investigate the effect of changing concentration on the rate of reaction by measuring the volume of gas given off?

A
  1. Measure 50 cm3 of 1.0 mol/dm3 H2SO4 solution into a flask
  2. Add the magnesium ribbon to the flask and connect it to the gas collection equipment
  3. Start the stopwatch and record the volume of gas every 10 seconds
  4. When the reaction is complete, repeat using 1.5 mol/dm3 sulfuric acid
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13
Q

What is the conclusion for the practical to investigate reaction rate by measuring gas volume?

A

As there are more reactant particles in a given volume collisions occur more frequently, increasing the rate of reaction

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14
Q

What is reaction rate important in?

A

The chemical industry and your body

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15
Q

What is Le Chateilier’s Principle?

A

Where you can change the relative amounts of the reactants and products in a reacting mixture at equilibrium by changing the conditions

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16
Q

What is collision theory?

A

The reacting particles do not only have to bump into each other but also need to colldie with enough energy to cause a reaction to take place

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17
Q

What is a catalyst?

A

A substance that changes the rate of a reaction without being changed chemically itself

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18
Q

What has a greater effect on the rate of reaction than the increased frequency of collisions?

A

An increased proportion of particles exceeding the activation energy

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19
Q

What happens when you heat ammonium chloride?

A

It’s broken down into ammonium gas and hydrogen chloride gas, but when the gases cool down they recombine to form the white solid ammonium chloride again

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20
Q

What happens when particles collide more frequently?

A

There are more chances for them to react, increasing the rate of reaction

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21
Q

What happens to catalysts used in chemical plants?

A

They can eventually become ‘posioned’ so they do not work anymore, because of the impurities in the reaction mixture which combine with the catalyst

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22
Q

What happens to a reversible reaction at equilibrium if the pressure is decreased?

A

The position of equilibrium will shift to favour the reaction that produces the most gas molecules

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23
Q

What happens to a reverisble reaction at equilibrium when the temperature is increased?

A

Position of equilibrium shifts in the endothermic reaction to cool the closed system down

24
Q

What happens if you change the coniditions for a reaction in equilibrium?

A

The position of equilibrium shifts in favour of the thing which has a lower amount of those conditions

25
Q

What happens if you add an alkali to HLit?

A

It turns into the Lit- ion by losing an H+ ion

26
Q

What happens if the forward reaction produces more molecules of gas?

A

An increase in pressure decreases the amount of products formed

27
Q

What happens if the forward reaction produces fewer molecules of gas?

A

An increase in pressure increases the amount of prodcuts formed

28
Q

What happens at equilibrium with a reversible reaction?

A

The rate of the forward reaction equals the rate of the reverse reaction

29
Q

What does Le Chatelier’s principle state?

A

If any of the conditions of a reversible reaction at equilibrium are changed, the system will adapt to counteract it.

30
Q

What does increased pressure do to the rate of reaction?

A

It squashes gas particles more closely together, increasing the chance they will collide and react

31
Q

What does a chemical reaction’s rate tell us?

A

How quickly reactants are converted into products

32
Q

What do the relative amounts of the reactants and products in a reversible reaction at equilibrium depend on?

A

The temperature

33
Q

What do many of the catalysts used in the industry involve?

A

Transition metals

34
Q

What colour is Lit-?

A

Blue

35
Q

What colour is HLit?

A

Red

36
Q

What colour change in heating copper sulfate crystals shows the change in the presence of water?

A

Blue to white

37
Q

What can the changes in conditions with Le Chateilier’s Principle be?

A

Concentration, pressure or temperature

38
Q

What can Litmus be represented as?

A

HLit

39
Q

What are the two ways you can work out the rate of a chemical reaction?

A

How quickly the reactants are used up and how quickly the products are made

40
Q

What are the two ways reactions are more likely to happen between reactant particles?

A

By increasing the frequency of reacting particles colliding with each other and increasing the energy you have when they collide

41
Q

What are the two reasons why raising temperature increases the rate of reaction?

A

Particles collide more often and particles collide with more energy

42
Q

What are the three techniques you can use to get the rate of a reaction?

A
  • Change in mass
  • Change in color
  • Increase/decrease in volume
43
Q

What are the four main factors which affect the rate of chemical reactions?

A
  • Temperature
  • Surface area
  • Concentration
  • Pressure
44
Q

What are catalysts normally used in the form of and why?

A

Powders, pellets or fine gauzes because these types of substances have high surface areas

45
Q

Particles that are moving around more quickly have more ___

A

energy

46
Q

In a reversible reaction, as the concentration of products builds up, the rate at which they react to re-form reactants ____

A

increases

47
Q

If a compound has water, what is it known as?

A

Hydrated

48
Q

If a compound has water removed, what is it known as?

A

Anhydrous

49
Q

How would you find the rate of reaction when reacting marble chips with hydrochloric acid?

A

By plotting the volume of carbon dioxide gas given off as the reaction progresses over time

50
Q

How do catalysts increase the rates of reactions?

A

By providing an alternative reaction pathway to the products with a lower activation energy than the reaction without the catalyst present. This means the frequency of effective collisions increases.

51
Q

How do catalysts help the environment?

A

Because using high temperatures and pressures often involves burning fossil fuels. So it stops carbon dioxide entering the atmosphere, combatting climate change

52
Q

How can you investigate the effect of changing concentration?

A

By reacting marble chips with different concentrations of hydrochloric acid

53
Q

How can you calculate the rate of a reaction at a given time?

A

Drawing a tangent to the curve at that point, constructing a right angled triangle and calculating the gradient

54
Q

Explain the effect that a cataluyst has on equillibrium

A
  • no effect
  • speeds up both foward and reverse
55
Q

Drawbacks of fast reactions

A
  • Safety concers
  • Expensive
56
Q
A