C5 Chemical Changes Flashcards
(22 cards)
What is an ore?
A rock that contains enough of a metal (compound) to be worth extracting
What is the reactivity series?
A list of elements ordered from the most to least reactive
What is the order of metals in the reactivity series?
Potassium
Sodium
Calcium
Magnesium
Aluminium
(CARBON)
Zinc
Iron
Tin
Lead
(HYDROGEN)
Copper
Silver
Gold
What happens in a displacement reaction?
A more reactive element will displace the less reactive element from its compound.
* e.g. Copper chloride + calcium → calcium chloride + copper
What is an ionic equation? How do you form one?
A chemical reaction in which the formulas of ionic, dissolved aqueous solutions are written as individual ions.
- Word equation
- Balanced symbol equation
- Total ionic equation (split out ions from ionic compounds)
- Net ionic equation (cross off spectator ions)
What do half equations show?
Half equations show what happens to individual reactants by loss or gain of electrons in a chemical reaction.
* e.g. Fe(s) → Fe2+ + 2e-
What is a redox reaction?
A reaction where both oxidation and reduction occur
What are oxidation and reduction?
Oxidation Is Loss of electrons
Reduction Is Gain of electrons
(OIL RIG)
How do you answer redox reaction questions?
Write half equations for the metal atoms becoming ions and vice versa. Identify which is oxidation and which is reduction
What is carbon used for?
Carbon is a common reducing agent, used to displace metals from their compounds. Carbon is a non-metal which is cheap and abundant.
What is a base? What is an alkali?
Base - anything that will neutralise an acid
* Metal oxides, Metal carbonates, metal hydroxides, ammonia
Alkali - a soluble base
* Metal Hydroxides, ammonia
What is the general equation for when a metal reacts with an acid?
Acid + metal → salt + hydrogen
(redox reaction)
What is the general reaction for when an acid reacts with a base?
Acid + base → salt + water
(neutralisation reaction)
What is the general reaction for when an acid reacts with a carbonate?
Acid + carbonate → salt + water + carbon dioxide
(neutralisation reaction)
What is the general reaction for when ammonia reacts with an acid?
Ammonia + acid → ammonium salt
(Neutralisation Reaction)
* e.g. Ammonia + nitric acid → ammonium nitrate, NH3 + HNO3 → NH4NO3
Describe a method to make pure, dry crystals of copper sulfate from a metal oxide and dilute acid
- Copper oxide reacts with sulfuric acid to make copper sulfate and water
- Use a measuring cylinder to measure 40cm^3 of sulfuric acid and pour into a beaker
- Use a tripod and gauze and a bunsen burner to gently warm the acid (30 secs)
- Remove acid from heat and add copper oxide to excess, stirring with a glass rod
- Filter out excess copper oxide using a funnel and filter paper into an evaporating basin leaving copper oxide as residue
- Heat (using a bunsen burner) until crystalisation point/half volume of solution evaporated.
- Leave in a warm place until the rest of the water has evaporated
- Pat crystals dry
What is the Ionic equation for a general neutralisation reaction?
H+(aq) + OH-(aq) → H2O(l)
What happens during a neutralisation reaction?
Acid molecules dissolve in water and ionise forming H+ ions, alkalis dissolve in water and ionise forming OH- ions.
The H+ from the acid reacts with the OH- from the alkali to produce water - H+(aq) + OH-(aq) → H2O(l)
What is an acid?
A substance that produces hydrogen ions when dissolved in water
What are some strong and weak acids? Why?
Strong - HCl, H2SO4, HNO3
Weak - Carbonic acid, Citric acid, ethanoic acid
Strong acids fully ionise in water whereas weak acids only partially ionise.
What is the relationship between pH and concentration of H+ ions?
The lower the pH, the higher the concentration of H+ ions.
As the pH increases by 1 unit, the H+ ion concentration of the solution decreases by a factor of 10.
What is the difference between strength and concentration of an acid?
Concentration tells us how many molecules of acid there are per unit of volume(dm^3). Strength tells us how much an acid ionises.
