acids, bases & salts Flashcards

1
Q

indicator

A

An indicator is a substance that is one colour in acids and a different colour in alkalis. they can be used either in solution or the solution can be dried on paper to make test papers.

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2
Q

universal indicator

A

universal indicator is a mixture of several different indicators. Universal indicator can indicate the strength of the acid or alkali

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3
Q

Red litmus paper

A

Red litmus paper turns blue when alkalise are added. it’s used to test for alkalis.

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4
Q

blue litmus paper

A

blue litmus paper turns red when acids are added. it is used to test for acids

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5
Q

The ph scale

A
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6
Q

understanding the PH scale

A

It is the hydrogen iron H that causes acidity. the pH scale is a measure of the concentration of hydrogen ions in solution and hence its acidity. So therefore, a solution of PH 1 contains 10x more hydrogen ions than a solution that has a pH 2. it is 10x as acidic. PH 1 is 100x more acidic than PH 3.

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7
Q

How to determine the ph of a solution precisely

A

by using a digital pH metre which can determine the PH to 1 or 2 d.p.

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8
Q

Acids

A

Acids can be regarded as a substance containing hydrogen and giving a pH of less than seven when dissolved in water.

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9
Q

Salts

A

Salts are a ionic substances where hydrogen is replaced by other positive ions (normally metals)
e.g. Mg + 2HCl → MgCl₂ + H₂

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10
Q

concentrated and dilute acids

A

refers to the amount of acid molecules dissolved in water a concentrated acid will have a high amount of acid molecules dissolved in a certain volume of water. a delete acid will have a relatively low number of acid molecules dissolved in the water.

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11
Q

strong and weak acids

A

refers to how many of the acid molecules have been split apart into ions this is called dissociation or ionisation

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12
Q

Strong acids (more detail)

A

strong acid will completely dissociate into its ions - all of the acid molecules have broken apart and formed into hydrogen ions. acid such as HCL, HNO₃ and H₂SO₄ are all strong acids. we can show that acid is fully dissociates by writing an equation – HCl ⇌ H+ + Cl-

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13
Q

weak acids (more detail)

A

In a weak acid only a small proportion of the molecules dissociate into ions this means the solution contains mainly undissociated compounds and just a low number of ions acids such as ethanoic acid, CH₃COOH all weak acids we can show that they only partially dissociate by writing an equation - CH₃COOH ⇌ CH₃COO- + H+

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14
Q

Bases

A
  • all substances whether soluble or not that neutralise acids.
  • normally metal oxides or metal hydroxides
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15
Q

alkali’s

A
  • subgroup of bases - also neutralise acids but must be soluble in water
  • generally soluble hydroxides
  • all alkalise will either dissolve in water or react with water to produce hydroxide ions (OH-) in solution. these ions cause alkalinity.
  • Like acids alkalise can also be concentrated or dilute and weak or strong
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16
Q

strong alkalise

A

strong alkalise like sodium hydroxide (NaOH) and potassium hydroxide can completely dissolve in water to give a high concentration of OH ions. – NaOH → Na+ + OH-

17
Q

Weak alkalise

A

weak alkalise like ammonia NH3 Only partially react with water giving a low concentration of OH- ions

18
Q

metal & acid rule

A

reactive metal + acid  metal salt + hydrogen
Magnesium + hydrochloric acid  magnesium chloride + hydrogen
Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)

19
Q

base & acid rule

A

base (alkali) + acid  metal salt + water
Copper oxide + nitric acid  copper nitrate + water
CuO(s) + 2HNO3(aq)  Cu(NO3)2(aq) + H2O(l)

20
Q

metal carbonate & acid rule

A

metal carbonate + acid  metal salt + water + carbon dioxide
Calcium carbonate + hydrochloric acid  calcium chloride + water + carbon dioxide
CaCO3(s) + 2HCl(aq)  CaCl2(aq) + H2O(l) + CO2(g)

21
Q

ammonia & acids rule

A

Ammonia + acid  ammonium salts
Ammonia + hydrochloric acid  ammonium chloride
NH3 + HCl  NH4Cl
NH3 + H+ -> NH4

22
Q

methyl orange

A

-pink in acids
-orange in neutral Solutions
-yellow in alkalis

23
Q

Phenolphthalein

A

-colourless in acids
-colorless in neutral Solutions
-pink in alkalis