40 terms

IGCSE Chemistry: Physical chemistry

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Terms in this set (...)

Acid
A substance that dissolves in water to produce hydrogen ions.
Base
A substance that dissolves in water to produce hydroxide ions.
Alkali
A base that is soluble in water.
Acidic solution
A solution that has a pH of less than 7.
Alkaline solution
A solution that has a pH of more than 7.
Litmus
An indicator that turns red from pH 0-5, purple from 5-8, and blue from 8-14.
Methyl orange
An indicator that turns red from pH 0-3, orange from 3-5, and yellow from 6-14.
Phenolphthalein
An indicator that turns colorless from pH 0-10 and red from 10-14.
Universal indicator
An indicator that changes color depending on the pH: red at pH 0, green at pH 7, and purple at pH 14. These color changes are gradual as the pH changes, so it goes through all the colors in the rainbow.
Salt
A compound formed when hydrogen ions in an acid are replaced by either a metal ion or by an ammonium ion.
HCl → H⁺ + Cl⁻
Ionization reaction of hydrochloric acid in water.
HNO₃ → H⁺ + NO₃⁻
Ionization reaction of nitric acid in water.
H₂SO₄ → 2H⁺ + SO₄²⁻
Ionization reaction of sulfuric acid in water.
Precipitation reaction
A reaction that produces a precipitate.
Precipitate
An insoluble solid that is made by a chemical reaction that takes place in an aqueous solution.
Titration
A method of finding out exactly the volume of one solution that is required to react with a given volume of another solution.
Rate of reaction
A measure of how fast a reaction occurs. Measured by the formula change in concentration of reactant divided by time.
Activation energy
The energy required for colliding particles to react.
Successful collisions
Collisions between particles that have the required activation energy.
Concentration
Increasing this will increase the number of particles of reactant in a given volume and hence the reacting particles will collide more often.
Temperature
Increasing this will increase the average kinetic energy of the reactant particles and therefore more of the collisions that take place will have the necessary activation energy to react.
Surface area
Increasing this will mean that there will be more particles of the solid exposed to the other reactant.
Catalyst
A substance that increases the rate of a chemical reaction by providing an alternative pathway for the reaction which has a lower activation energy than the original pathway. The substance remains chemically unchanged at the end of the reaction.
Excess base
A method of preparing soluble salts from acids.
Salt, water
Products when reacting an acid with a metal hydroxide.
Salt, water, carbon dioxide
Products when reacting an acid with a metal carbonate.
Salt, water
Products when reacting an acid with a metal oxide.
Salt, hydrogen
Products when reacting an acid with a metal.
Exothermic reaction
A reaction in which heat is released.
Endothermic reaction
A reaction which absorbs heat from the surroundings.
Molar enthalpy change
The amount of energy released or absorbed by a reaction can be measured experimentally using this equation.
Bond energy
The energy required to break a bond. Usually measured in kilojoules per mole of bonds (kJ/mol).
Closed system
No substances are added to the reaction mixture and no substances escape from it.
Dynamic equilibrium
The amount of reactants and products stays the same. There appears to be no change. However, the amount of reactants and products are not necessarily equal to each other.
Forward reaction is favored
When there is more product than reactant. This is usually what we want.
Reverse reaction is favored.
When there is more reactant than product. This is usually not what we want.
Decreases
What happens to the product yield if the forward reaction is exothermic and the temperature is increased?
Increases
What happens to the product yield if the forward reaction is exothermic and the temperature is decreased?
Increases
What happens if the forward reaction is endothermic and the temperature is increased?
Decreases
What happens if the forward reaction is endothermic and the temperature is decreased?