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LGS GCSE OCR Chemistry A > C3 Chemical Reactions > Flashcards

C3 Chemical Reactions Flashcards

1
Q

Exothermic

A

Gives out energy. Usually in the form of heat, is shown with a rise in temperature.

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2
Q

Exothermic Example

A

Burning Fuels.

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3
Q

Endothermic

A

Takes in energy. Usually in the form of heat, is shown with a fall in temperature.

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4
Q

Endothermic Example

A

Thermal Decomposition.

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5
Q

Bond Breaking

A

Requires energy, so is Endothermic. Energy required to break bonds is greater than energy used in breaking old bonds.

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6
Q

Bond Making

A

Energy is released when formed, is Exothermic. Energy released is greater than energy used in breaking old bonds.

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7
Q

Specific Heat Capacity (SHC)

A

Amount of energy required to raise the temperature of 1 gram of a substance by 1 celcius.

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8
Q

Calorimetric

A

An experiment involving heating water by burning liquid fuel.

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9
Q

Energy given out per gram

A

Energy Released / Mass of Fuel Burnt.

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10
Q

Example of a Slow Reaction

A

Rusting

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11
Q

Example of a Fast Reaction

A

Explosion

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12
Q

How could you measure gas production?

A

Change in mass, or Gas Syringe.

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13
Q

Reaction Rate

A

The speed of reatants being turned into products.

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14
Q

Collision Frequency

A

How often particles collide during a reaction. More collisions - Higher reaction rate.

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15
Q

Energy Transfer during Collision

A

Particles need enough energy for a collision to be successful.

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16
Q

Yield

A

The amount of product you get from a reactant.

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17
Q

Limiting Reactant

A

The reactant which runs out first, stopping the reaction.

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18
Q

Excess Reactant

A

The other reactant which didn’t stop the reaction - some of this left.

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19
Q

Higher Temperature

A

Increases Reaction Rate (Faster)

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20
Q

Higher Concentration

A

Increases Reaction Rate (Crowded)

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21
Q

More Surface Area

A

Increases Reaction Rate (Reachability)

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22
Q

Catalyst

A

Increases Reaction Rate, by facilitating a surface for reactants to stick to. Increases successful collisions not collision frequency.

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23
Q

Relative Atomic Mass

A

Total atomic mass of an element

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24
Q

What is spectroscopy?

A

The study of the colour of flame given off by a substance when it is heated. Certain elements produce distinctly coloured flames when heated, which in turn create line spectra. This could aid with the discovery of new elements.

Lithium - Red , Sodium - Orange , Potassium - Lilac

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25
Q

Why must equations be balanced?

A

In a chemical reaction, the mass of the reactants is always equal to the mass of the products, because no atoms are lost or made. This means there needs to be the same number of atoms for each element either side of the equation.

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26
Q

=

A

Double bond

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27
Q

-

A

Single bond

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28
Q

Ionic equations

A

Formulas of ions that make precipitate and precipitate + state symbols + charge and balanced.

29
Q

Reduction reactions

A

Where a metal is separated from minerals where it has combined with other elements.

30
Q

Reducing agent

A

A chemical that removes oxygen from another chemical. Such as carbon to a metal oxide.

31
Q

When a reagent is added?

A

It is oxidised.

32
Q

Extracting Aluminium - Aluminium forms at the

A

Negative Electrode

33
Q

Extracting Aluminium - Oxygen forms at the

A

Positive electrodes

34
Q

Electrolysis of aluminium

A

Molten electrolyte is contained in a steel tank lined with carbon. The carbon lining is the negative electrode. Positive electrodes are inserted. Molten aluminium forms a pool in the bottom.

35
Q

Extracting Aluminium - The electric current

A

Decomposes the electrolyte.

36
Q

On the pH scale, what numbers are acids?

37
Q

On the pH scale, what number is neutral?

38
Q

On the pH scale, what numbers are alkali?

39
Q

What do the colours on the pH scale show?

A

They are the colours that you will get if you were to add a universal indicator to an acid or an alkali solution

40
Q

Give some examples of acidic products

A

Citric acid, used as a food acid. Solid

Ethanoic acid, the acid in vinegar. Liquid

Hydrogen chloride. Gas

41
Q

Give some examples of alkali products

A

Sodium hydroxide, used to make bleach

Potassium hydroxide, used in alkaline batteries

Calcium hydroxide, used to neutralise acidic soils

42
Q

What two methods/tools can be used to determine pH?

A

Indicators and pH meters

43
Q

How does litmus paper determine pH?

A

Easiest method to determine whether a solution is acidic or alkaline. Turns red if the solution is acidic and blue if its alkaline

44
Q

How does a universal indicator determine pH?

A

A useful combination of dyes, which gives the colours shown in the pH scale. It is useful for estimating the pH of a solution

45
Q

How does a pH meter determine pH?

A

A probe which is dipped into the substance, and a meter will give a reading of the pH

46
Q

What is a more accurate method, indicators or pH meters?

47
Q

What is a neutralisation reaction?

A

When the products created are neutral

48
Q

Give the equation for a neutralisation reaction

A

Acid + Alkali —> Salt + Water

49
Q

Acidic compounds produce what in water?

A

Aqueous hydrogen ions

50
Q

Alkali compounds produce what in water?

A

Aqueous hydroxide ions

51
Q

What is the typical equation for reacting an acid and a metal together?

A

Acid + Metal —> Salt + Hydrogen

52
Q

Give a neutralisation reaction using a metal oxide

A

Acid + Metal Oxide —> Salt + Water

53
Q

Give a neutralisation reaction using a metal hydroxide

A

Acid + Metal Hydroxide —> Salt + Water

54
Q

Give a neutralisation reaction using a metal oxide using specific elements

A

Hydrochloric acid + Copper oxide —> Copper chloride + water

55
Q

Give a neutralisation reaction using a metal hydroxide using specific elements

A

Hydrochloric acid + Sodium hydroxide —> Sodium chloride + Water

56
Q

Give a neutralisation reaction using a metal carbonate

A

Acid + Metal Carbonate —> Salt + Water + Carbon dioxide

The same as all the other neutralisation reactions, except carbon dioxide is given off from the carbonate as well

57
Q

What are the three steps to measuring masses in reactions?

A
  1. Balance the equation
  2. Work out M (relative formula mass), and multiply by the number in front of the formula
  3. You’ll get for example 48g of Mg reacts to give 80g of MgO. So, you need to divide to get how much is required to get 1g of MgO, then multiply to get the desired amount
58
Q

What are titrations?

A

Used to check purity of acidic or alkaline products by using neutralisation reactions

59
Q

Describe the process of titrations

A
  1. Add a known volume of alkali to a titration flask, along with 3 drops of indicator
  2. Fill the burette with acid
  3. Release the acid from the burette into the alkali a bit at a time, swirling the conical flask at the base to ensure the two become mixed completely
  4. Go slow when you think the end point (colour change) is about to be reached so that the alkali does not skip past neutralisation
  5. The indicator changes colour when ALL of the alkali has been neutralised
  6. At this stage, record the volume of acid used to neutralise the alkali

Can also be done the other way around, adding alkali to acid

60
Q

Titrations cannot be carried out with _____, only _____. What does this mean?

A

Cannot be carried out with solids, only liquids. This means any solid alkali or acid being tested has to be made into a solution first

61
Q

Describe the process preparing a solid for titration

A
  1. If the substance is a solid lump, crush into powder
  2. Put titration flask onto a balance
  3. Weigh some of the powder into the flask
  4. Ass a solvent, e.g water or ethanol to dissolve the powder
  5. Swirl the titration flask until the solid dissolves
62
Q

What is the equation for calculating for mass?

A

Mass = concentration x volume

63
Q

What is the equation for calculating percentage purity?

A

Calculated mass of substance

——————————— x 100

Mass of impure substance at start

64
Q

What is an exothermic reaction?

A

One which GIVES OUT energy to the surroundings, usually in the form of heat, and usually shown by a rise in temperature

E.G Fuels burning or Neutralisation reactions

65
Q

What is an endothermic reaction?

A

One which TAKES IN energy from the surroundings, usually in the form of heat, and usually shown by a fall in temperature

E.G Photosynthesis

66
Q

Describe an energy level diagram for an exothermic reaction

A

Products at a lower energy than reactants

Difference in height represents the energy given off by the reaction

67
Q

Describe an energy level diagram for an endothermic reaction

A

Products at a higher energy than the reactants

Difference in height represents the energy taken in during the reaction

68
Q

In the chemical industry, if a chemical synthesis reaction is exothermic, what must be controlled in order to ensure products remain unaffected?

A

Heat produced has to be removed, otherwise the temperature of the reaction mixture will increase

Temperature increase will increase the rate of reaction and the reaction mixture will get even hotter

If the reaction mixture becomes too hot then some of the reactants or products could become gases, increasing pressure and causing an explosion

69
Q

In the chemical industry, if a chemical synthesis reaction is endothermic, what must be controlled in order to ensure products remain unaffected?

A

Heat must be provided to the reaction, otherwise the reaction mixture might become too cold

This could slow down the rate of reaction or cause the reaction mixture to freeze, which could damage equipment and stop the whole process

LGS GCSE OCR Chemistry A (9 decks)

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