Acids & Bases Flashcards
Give the equation of the dissociation of water molecules.
H₂O ⇌ H⁺ + OH⁻
How do you name a salt?
The 1st part of the name comes from the 1st part of the base.
The 2nd part of the name comes from the type of acid. Eg: hydrochloric acid = chloride,
nitric acid = nitrate, phosphoric acid = phosphate, sulfuric acid = sulfate
Eg: copper oxide + nitric acid → copper nitrate + water
What does ⇌ mean?
⇌ means that a reaction is reversible.
Why is water a neutral substance?
Water is a neutral substance because it has an equal concentration of H⁺ and OH⁻ ions.
How you do carry out volumetric titration?
It involves reacting an acid with a base.
What three groups do chemicals fall under (in terms of pH)?
- neutral
- acidic
- basic
What is a standard solution?
A solution of accurately known concentration.
What makes substances acidic?
Acidic substances have a higher concentration of H⁺ ions to OH⁻ ions.
What is the definition of concentration?
Concentration is the measure of the amount of solute dissolved in a certain volume of solvent. It is measured in mol/l.
What is the formula for concentration?
n=cV
n = number of moles
c = concentration (mol/l)
V = volume (litres) (VOLUME MUST BE IN LITRES, TO CHANGE FROM CM3, DIVIDE BY 1000)
What makes substances basic?
Basic substances have a higher concentration of OH⁻ ions to H⁺ ions.
How can we tell acidic, basic and neutral substances apart?
We can use an indicator. An indicator is a chemical which changes colour depending on the acidity of what is being tested.
(examples include: red cabbage, universal indicator, pH paper)
Example calculation: Calculate the mass of NaOH which is needed to make 200cm3 of a 4 mol/l solution.
Step 1: Calulate number of moles
n=cV
n= 4x0.2
n= 0.8 moles
Step 2: calculate mass
m=nxGFM
m= 0.8x40
m= 32g
The mass of NaOH is 32g
What are the names of common acids?
- hydrochloric acid: HCl / H⁺Cl⁻
- sulfuric acid: H₂SO₄ / (H⁺)₂SO₄²⁻
- nitric acid: HNO₃ / H⁺NO₃⁻
- phosphoric acid: H₃PO₄ / (H⁺)₃PO₄³⁻
- citric acid
- ascorbic acid (vitamin C)
What are the steps of a titration calculation?
- Calculate the number of moles (n) using n=cV for the reactant whose concentration and volume is given.
- Use mole ratio to find the number of moles of the other reactant.
- Calculate the unknown (either c or V) using either c=n/V or V=n/c
How can an acid be made?
non-metal oxide + water → acid
examples include: sulfur dioxide + water → sulfuric acid
nitrogen oxide + water → nitric acid
SO₂ + H₂O → H₂SO₄
NO + H₂O → HNO₃
Example calculation: Calculate the concentration of NaOH if 100cm3 of NaOH is neutralised by 50cm3, 2 mol/l H₂SO₄
H₂SO₄ + 2NaOH → Na₂SO₄ + H₂O
- n=cV 2. 1 mole : 2 moles
n=2x0.05. 0.1 moles : 0.2 moles
n=0.1moles H₂SO₄ - c= n/V
c= 0.2/0.1
c= 2 mol/l
The concentration of NaOH is 2 mol/l.
What kind of salts does neutralisation produce?
Soluble salts
How are insoluble salts made?
Insoluble salts are made from precipitation.
Eg: Barium chloride (aq) + sodium sulfate (aq) → Barium sulfate (s) + Sodium chloride (aq)
(the precipitate)
Note: check pg 8 of the data book for Solubilities of Selected Compounds in Water
What are the names of common bases?
- sodium hydroxide: NaOH / Na⁺OH⁻
- potassium hydroxide: KOH / K⁺OH⁻
- sodium carbonate: Na₂CO₃ / (Na⁺)₂CO₃²⁻
How do you make an alkali?
metal oxide + water → metal hydroxide
What are the three types of base?
- metal oxides
- metal hydroxide
- metal carbonate
What is neutralisation?
It is the reaction of an acid with a base
How can acids and bases be neutralised?
- acid + metal oxide → salt + water
- acid + metal hydroxide → salt + water
- acid + metal carbonate → salt + water + carbon dioxide
Examples include:
hydrochloric acid + sodium hydroxide → sodium chloride + water
HCl + NaOH → NaCl + H₂O
sulfuric acid + sodium hydroxide → sodium sulfate + water
H₂SO₄ + NaOH → Na₂SO₄ + H₂O
phosphoric acid + sodium hydroxide → sodium phosphate + water
H₃PO₄ + NaOH → Na₃PO₄ + H₂O
Note: the acid and base should be of opposing strength
(example: if HCl = pH 1 then NaOH = pH 13)
