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Chemistry Year 3/4 > Chapter 4 ( Acids And Alkali ) > Flashcards

Chapter 4 ( Acids And Alkali ) Flashcards

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1
Q

What is an acid?

A

An acid is a substance that produces hydrogen ions, H+, in aqueous solutions.

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2
Q

When does H+ form?

A

When hydrogen loses its one electron it becomes a cation with 1 proton only

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3
Q

Why is water present in order for acids to work?

A

Water must be present to ionise the acid and make it form and release H+ ions which are responsible for the acidic properties of an acid.

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4
Q

How is hydrochloric acid formed?

A

Hydrogen chloride dissolves in water to form aqueous hydrochloric acids which produce H+ ions responsible for acidic properties letting hydrogen chloride become hydrochloric acid

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5
Q

Formula of hydrochloric acid nitric acid and ethanoic acid?

A

HCl

HNO3

CH3COOH

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6
Q

What are the properties of acids?

A

Sour taste
Conduct electricity
Red litmus paper colour
React ONLY with reactive metals
React with bases = neutralisation
React with carbonates = form a salt, water, C02

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7
Q

Why do you think acids can conduct electricity?

A

In order for an acid to have its acidic properties it needs to be ionised in water forming an aqueous solution where ions can act as mobile charged carriers IN THE SOLUTION and hence conduct electricity

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8
Q

What words indicate an aqueous solution?

A

Diluted, solution

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9
Q

Can acids react with all metals? Which metals can it or can it not?

A

Acids only react with reactive metals like magnesium ribbon.

NOT like copper silver gold

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10
Q

What happens when an acid reacts with a reactive metal?

A

Salt and hydrogen gas is formed

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11
Q

What happens when acids react with bases and what occurs + produced?

A

When acids react with bases or alkalis, salt and water is formed and neutralisation occurs where the solution obtains a neutral pH

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12
Q

How do you write the salt?

A

First reactant on LHS ( which should be acid ) FIRST ELEMENT LENA so Like from So4C5 take the entire chunk of SO4 ( make sure you take the 4 ) and then second reactant ka last element lo and combine as a salt

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13
Q

What are stains? And how to remove?

A

Hard water stains are calcium carbonate so hence acids are used to remove these hard water stains because acids can react with carbonates

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14
Q

What happens when acids react with carbonates?

A

Salt water CO2 formed

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15
Q

How do you know that an acid has reacted with a carbonate?

A

The gas released by the mixture should be transferred into tube of limewater and if white precipitate forms, carbon dioxide present and acid reacted with carbonate

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16
Q

What is the strength of an acids dependant on?

A

Depends on the extent of ionisation of an acid when dissolved in water

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17
Q

What is a strong acid?

A

A strong acid is an acid that is completely ionised in aqueous solution. ALL the acid molecules have undergone ionisation to form ions AND ACID FORMS HIGH CONCENTRATION OF H+ IONS

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18
Q

What is a weak acid?

A

A weak acid is an acid that is only partially
ionised in an aqueous solution. Only a few
acid molecules ionised in aqueous
solutions. ACID FORMS LOW CONCENTRATION OF H+ IONS

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19
Q

What does forward arrow represent of acid strength?

A

represents a reaction that proceeds in only one
direction, hence complete ionisation signalling it’s a strong acid.

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20
Q

What does reversible arrow mean about an acid?

A

represents a reaction that proceeds in both directions,
hence the partial ionisation of the weak acid.

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21
Q

What is a mono basic acid?

A

Monobasic acids produce 1 unit of H+ when 1 unit of the acid molecule is ionised

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22
Q

What are Dibasic acids?

A

produce 2 unit of H+ when 1 unit of acid molecule is ionised.

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23
Q

Which type of acid is stronger?

A

Dibasic acids as they form and release a higher concentration of H+ ions than mono basic acids Helen making them stronger acids.

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24
Q

What is the concentration of acid referring to?

A

The concentration of an acid refers to the amount of it per unit volume.

25
Q

Does it mean a more concentrated acid = stronger?

A

MISOCNCEPTION. acid strength dependant on the amount of H+ ions its produces when ionised in aqueous solution of water.

26
Q

What are bases?

A

All metal oxides or hydroxides are bases. Anything saying oxide or ide is a base

27
Q

How can I find acid based on its name?

A

Acids have the word acid behind them

28
Q

Are alkali and bases the same thing?

A

NO. bases that are soluble in water form alkalis hence alkalis are bases that are soluble in water

29
Q

So what’s the definition of a base?

A

Substance that reacts with acid and causes neutralisation

30
Q

What does an alkali do apart from neutralisation?

A

An alkali dissociates in water and produces hydroxide ions ( OH- )

31
Q

What are examples of alkali which are soluble?

A

Group 1 metal hydroxides and barium hydroxide are soluble. Calcium hydroxide is partially soluble.

32
Q

What makes a strong alkali? + pH

A

An alkali that is completely ionised in aqueous solution to form a high concentration of OH- ions.

pH 11 to 14

33
Q

What makes a weak alkali and what’s the ph

A

An alkali that is partially ionised in aqueous
solution to form a low concentration of OH-
ions.

ph 8 to 10

34
Q

Alkali properties?

A

Bitter taste
Feel slippery and soapy
Conduct electricity
Blue litmus colour
React with acids in neutralisation reaction
React with ammonium salts
Make metal hydroxides to precipitate

35
Q

Why do you think alkali can conduct electricity?

A

Alkalis produce hydroxide ions when
dissolved in water. These ions allow the resulting aqueous solution to conduct electricity as they act as mobile charged carriers.

36
Q

Ammonia and Ammonium !!

A

Ammonia = NH3
Ammonium = NH4

37
Q

What happens when alkalis react with ammonium salt?

A

Salt, water and ammonia is formed.

38
Q

How do I know it’s ammonia?

A

Damp litmus paper turns blue in the presence of ammonia

39
Q

Property of metal hydroxides?

A

Most are insoluble in water

40
Q

What happens when alkali + metal hydroxides

A

The addition of alkali to a solution of most metal ions causes the precipitation of the insoluble hydroxides.

41
Q

What colour is precipitate

A

Different colours so must state

42
Q

When alkali + metal hydroxides what happens to products?

A

To write the products, keep the first word of reactants like copper, and then the second word of each substance just switch

So copper sulfate + sodium hydroxide =

Copper hydroxide + sodium sulfate ( in ppm form )

43
Q

Methyl orange in acid and alkali? What ph it changes at

A

Red in acid, yellow in alkali changes in colour at 3 to 5 ph rang

44
Q

Litmus in acid and alkali is what colour at what pH?

A

Litmus red in acid, blue in alkali, 5 to 8 ph colour changes

45
Q

Thymolphtalein acid and alkali and pH?

A

PH: 9 to 10.5 can see indicator colour changes
Acid : colourless
Alkali: blue

46
Q

Screened methyl orange acid alkali and PH colour chnage

A

pH: 3 to 5
Acid: violet
Alkali: green

47
Q

Which indicator do I use and what’s their property?

A

The type of indicator to use will depend on the pH changes in the reaction.

Indicators do not take part in the chemical reaction.

48
Q

What happens when pH lesser than 7?

A

H+ ion concentration more than OH- ions so acid presence is stronger than alkali presence

49
Q

What happens at ph 7?

A

The concentration of H+ ions is the same as that of OH– ions.

50
Q

What happens at pH more than 7?

A

The concentration of H+ ions is lower
than that of OH– ions. Stronger presence of alkali than acid

51
Q

How to measure pH of a solution?

A

Ph meter or pH sensor

52
Q

Why do we need indicators

A

Tells us pH of substances to differentiate acids from alkali and bases

53
Q

How do we know which substance do we write first in equation?

A

Alphabetical order

54
Q

What can affect plant growth

A

Soil pH affects how much nutrients a plant can absorb

55
Q

How to reduce soil acidity and how does it work?

A

Liming. By using slaked limed aka calcium hydroxide or quick lime calcium oxide, neutralisation occurs with acids increasing soil pH

56
Q

Optimum soil pH?

A

Neutral to slightly acidic

57
Q

What is an essential element in plant growth?

A

Nitrogen

58
Q

Ingredients in fertilisers?

A

Nitrogen and Ammonia ( NH3 )

Chemistry Year 3/4 (5 decks)

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