C5 - Chemical Changes Flashcards
What is an acid?
When dissolved in water, its solution has a pH value less than 7. Acids release H+ ions when added to water
What is an alkali?
When dissolved in water, its solution has a pH value more than 7. Alkalis release OH- ions when added to water
What is a base?
the oxide, hydroxide, or carbonate of a metal that will react with an acid and be neutralised, forming a salt + water
What is a displacement reaction?
a reaction in which a more reactive element takes the place of a less reactive element in one of its compounds or in solution
What is electrolysis?
the breakdown of a substance containing ions by electricity
What is equilibrium?
the point in a reversible reaction at which the forward and backward rates of reaction are the same. Therefore, the amounts of substances present in the reacting mixture remain constant
What is a half equation?
an equation that describes reduction (gain of electrons) or oxidation (loss of electrons)
What is an ionic equation?
an equation that shows only those ions or atoms that change in a chemical reaction
What is a metal ore?
a rock that contains enough of a metal or metal compound that it is worth extracting the metal
What is neutral?
a solution with a pH value of 7 which is neither acidic nor alkaline.
What is neutralisation?
the chemical reaction of an acid with a base in which a salt and water are formed. If the base is a carbonate or hydrogen carbonate, carbon dioxide is also produced in the reaction
What is an ore?
a rock which contains enough metal to make it economically worthwhile to extract the metal
What is oxidation/oxidised?
a reaction where oxygen is added to a substance / or when electrons are lost from a substance
What is pH?
a number which shows how strongly acidic or alkaline a solution is
What is the reactivity series?
a list of elements in order of their reactivity
What is reduction / reduced?
a reaction in which oxygen is removed or electrons are gained
What is a salt?
an ionic compound (can be formed when an acid reacts with a base)
What are strong acids?
these acids completely ionise in aqueous solutions
What are weak acids?
acids that do not dissosiate completely in aqueous solutions
What are 3 strong acids?
- Hydrochloric Acid
- Sulfuric Acid
- Nitric Acid
What is an example of a weak acid?
*Ethanoic Acid
What is the formula of Hydrochloric Acid
HCl
What is the formula of Sulfuric Acid
H₂SO₄
What is the formula of Nitric Acid
HNO₃
What is the formula of Ethanoic Acid
CH₃COOH
What is the equation for Hydrochloric Acid ionising?
HCl -> H⁺ + Cl⁻
What is the equation for Sulfuric Acid ionising?
H₂SO₄ -> 2H⁺ + SO₄²⁻
What is the equation for Nitric Acid ionising?
HNO₃ -> H⁺ + NO₃⁻
What is the equation for Ethanoic Acid ionising?
CH₃COOH ⇌ H⁺ + CH₃COO
What is the equation for an acid reacting with a metal oxide?
acid + metal oxide → salt + water
What is the equation for an acid reacting with a metal hydroxide?
acid + metal hydroxide → salt + water
What is the equation for an acid reacting with a metal carbonate?
acid + carbonate → salt + water + carbon dioxide
What type of salt is produced with sulfuric acid?
sulfate
What type of salt is produced with nitric acid?
nitrate
What type of salt is produced with hydrochloric acid?
chloride
What would be the typical PH of a strong concentrated acid?
0 or 1
What would be the typical PH of a strong dilute acid?
2 or 3
What would be the typical PH of a weak concentrated acid?
4 or 5
What would be the typical PH of a weak dilute acid?
5 or 6
What would be the reaction with magnesium of a strong concentrated acid?
vigorous fizzing
What would be the reaction with magnesium of a strong dilute acid?
fizzing
What would be the reaction with magnesium of a weak concentrated acid?
gentle fizzing
What would be the reaction with magnesium of a weak dilute acid?
hardly any fizzing
What colour would the universal indicator be with a strong concentrated acid?
red
What colour would the universal indicator be with a strong dilute acid?
red
What colour would the universal indicator be with a weak concentrated acid?
orange
What colour would the universal indicator be with a weak dilute acid?
yellow
What proportion of molecules would react with water to for H⁺ with a strong concentrated acid?
all
What proportion of molecules would react with water to for H⁺ with a strong dilute acid?
all
What proportion of molecules would react with water to for H⁺ with a weak concentrated acid?
few
What proportion of molecules would react with water to for H⁺ with a weak dilute acid?
few
How do you identify an acid?
It will contain H⁺ in its formula (i.e. HCl or H₂SO₄)
How do you identify an alkali?
It will contain OH- in its formula (i.e. NaOH or KOH)
How do you identify a base?
It will contain oxide (O), carbonate (CO₃²⁻), or hydroxide (OH-) (i.e. MgO or PbCO₃)
How do you identify a salt?
It will be the product of an acid base reaction, (i.e. Potassium Nitrate or Zinc Chloride)
Can an acid be a base?
no
Can an alkali be a base?
yes
Can a salt be a base?
no
What happens in a neutralisation reaction between an acid and an alkali?
Hydrogen ions react with hydroxide ions to produce water
What is the equation for the neutralisation of an acid with an alkali?
H+(aq) + OH-(aq) → H2O(l)
What are bases that are soluble in water called?
alkalis
What are substances that can be used to identify alkalis and acids called?
indicators
What colour does methyl orange turn in a strong acid?
red
What colour does methyl orange turn in a weak acid?
red
What colour does methyl orange turn in water?
orange
What colour does methyl orange turn in a weak alkali?
yellow
What colour does methyl orange turn in a strong alkali?
yellow
What colour does Phenolphthalein solution turn in a strong acid?
colourless
What colour does Phenolphthalein solution turn in a weak acid?
colourless
What colour does Phenolphthalein solution turn in water?
colourless