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IGCSE Chemistry > Physical Chemistry > Flashcards

Physical Chemistry Flashcards

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1
Q

Describe the pH levels

A
  • pH 1-4: strongly acidic
  • pH 4 - 6: weakly acidic
  • pH 7: neutral
  • pH 8-9: weakly acidic
  • pH 10-14: strongly alkaline
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2
Q

How do you determine the pH of a solution?

A
  • universal indicators
  • litmus paper: red in acidic solutions, purple in natural and blue in alkaline solutions
  • phenolphthalein: colourless in acidic solutions and in weak alkaline, it is pink and in strong alkaline, it is pink/purple
  • methyl orange: changes from red in acidic solution to orange-yellow in weak acid, to yellow in alkaline
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3
Q

What is an acid?

A
  • a source of hydrogen ions (H+)

- pH less than 7

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4
Q

What is a base?

A
  • a substance that can neutralise and acid

- alkalis are soluble bases

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5
Q

What is an alkali?

A
  • a source of hydroxide ions (OH-)

- pH greater than 7

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6
Q

What is the reaction between an acid and base called?

A
  • a neutralisation reaction
  • acid + base = salt + water
  • H+(aq) + OH-(aq) = H2O
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7
Q

acid + metal oxide =

A
  • acid + metal oxide = salt + water
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8
Q

acid + metal =

A

-acid + metal = salt + hydrogen

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9
Q

acid + metal carbonate =

A

acid + metal carbonate = salt + water + carbon dioxide

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10
Q

acid + metal hydroxide =

A

acid + metal hydroxide = salt + water

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11
Q

What are the solubility rules?

A
  • all common sodium, potassium and ammonium salts are soluble
  • all nitrates are soluble
  • all chlorides are soluble except for silver chloride
  • all sulphates are soluble except for barium and calcium sulphate
  • all carbonates are insoluble except for sodium, potassium and ammonium carbonates
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12
Q

How to make and purify a soluble salt (a pure dry sample)?

A
  • e.g. sulphuric acid + copper oxide = water + copper sulphate
  • warm the acid to about 50 degrees
  • spoon copper oxide and dissolve it
  • make it dissolve in excess
  • warm to about 70 degrees, add more copper oxide, if cannot dissolve, all acid has been reacted
  • filter through filter paper into an evaporating basin
  • gently boil until a third is left, not all because there may be thermal decomposition
  • leave to crystallise. leave it in a warm place or desiccator
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13
Q

How do you make an insoluble salt?

A
  • a precipitation reaction
  • mix the two solutions
  • separate with a funnel and filter paper
  • it is not pure if you dry immediately because some of the filtrate will be left in the residue as impurities. rinse with dilute water
  • dry in desiccator or evaporate slowly
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14
Q

How do you do titration?

A
  • using a pipette, add some alkali (about 25cm^3) to a conical flask, along with two or three drops of indicator
  • fill a burette with the acid, below eye level
  • using the burette, add the acid to the alkali a bit at a time, given the conical flask a swirl
  • indicator changes colour when all the alkali has been neutralised
  • record the volume of the acid
  • repeat for more reliable results
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15
Q

What four things do the rate of reaction depend?

A
  • pressure/concentration
  • temperature
  • catalyst
  • surface area
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16
Q

What is the equation for rate of reaction?

A
  • rate of reaction = amount of reactant used or amount of product formed / time
17
Q

How can you measure the rate of reaction?

A
  • precipitation: observe a marker through the solution and measure how long it takes to disappear.
  • change in mass: most accurate method. cotton wool used to prevent spitting of the HCl, so that mass does not reduce
  • volume of gas: using a gas syringe to measure the volume of gas given off
18
Q

Describe different rate of reaction experiments

A
  • hydrochloric acid and marble chips: for surface area.
    measure volume of gas at regular herbals
  • magnesium with HCl: for concentration
  • sodium thiosulfate and HCl: for temperatures. colourless to react to form yellow precipitate of sulphur.
  • decomposition of hydrogen peroxide: for catalyst
19
Q

How does higher temperature increase rate of reaction?

A
  • particles have more kinetic energy
  • so more frequent collisions
  • and a higher proportion of collisions have activation energy,
  • so more successfully collisions
20
Q

How does higher concentration or pressure increases rate of reaction?

A
  • there are a greater amount of particles in a the same space
  • therefore, more frequent collisions
21
Q

How does larger surface area increase rate of reaction?

A
  • particles will have more area to work on, more sites for potential collision to occur
  • more frequent useful collisions
22
Q

How do catalysts increase rate of reaction?

A
  • increase the rate of reaction by providing an alternative route of reaction with lower activation energy. a greater proportion of collisions will have sufficient energy to result in reaction

IGCSE Chemistry (10 decks)

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