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Metal Carbonates
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when metal carbonates decompose they form a metal oxide and carbon dioxide gas.
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eg. when solid green copper carbonate is heated, a black solid and a colourless gas is formed. The gas turns limewater cloudy when bubbled through it.
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copper carbonate --> copper oxide + carbon dioxide
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an exception of this rule is silver carbonate, which decomposes to form silver metal, carbon dioxide, and oxygen.
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Metal Hydroxides
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when metal hydroxides decompose they form a metal oxide and water.
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eg. when solid white calcium hydroxide is heated, a white solid and a colourless liquid is formed. The liquid turns blue cobolt chloride paper pink.
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calcium hydroxide --> calcium oxide + water
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Metal Hydrogen Carbonates (bicarbonates)
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when metal hydrogen carbonates decompose they form a metal carbonate, carbon dioxide, and water.
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eg. sodium bicarbonate --> sodium carbonate + carbon dioxide + water
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Catalytic Decomposition
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a catalyst reduces the amount of energy needed for a reaction to proceed. They allow reactions to take place at room temperature that would otherwise require higher temperatures.
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Hydrogen peroxide: the decomposition can be sped up by the catalyst manganese dioxide (MnO₂).
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Chemical reactions where the atoms of one element react with the atoms of another element to form a single compound.
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element A + element B --> element AB
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Combination Reactions with Oxygen
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-sometimes called oxidation reactions
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-when heat/light is produced it is also known as combustion/burning
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-the product is more stable than the reactants
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-can have a unique flame colour (see important observations)
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Ionic Compounds
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when metal elements combine with non-metal elements.
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-valence electrons are transferred from the metal to the non-metal
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-the metal forms a positive ion and the non-metal forms a negative ion
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-the ions are held together by electrostatic forces of attraction (positive-negative)
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Covalent Compounds
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when non-metals combine with other non-metals.
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-bonding electrons are shared so that each atom has a stable full valence electron shell
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Protons
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positive charge, large mass, in the atom nucleus, top left number
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Neutrons
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neutral charge, large mass, in the atom nucleus, subtract the number of protons from the bottom right number
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Electrons
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negative charge, very tiny mass, in the outer shells, top left number
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Anion
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negatively charged ion
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Cation
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positively charged ion
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The number of protons deciphers the atom. The number of neutrons can change to create isotropes.
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When forming equations, always put the cation first eg. Na + Cl --> NaCl not ClNa
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'During a chemical reaction matter cannot be created nor destroyed.'
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This is the law of conservation of mass.
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This means that the reactants and products shown in a chemical equation must balance.
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Eg. 4Fe +3O₂-->2Fe₂O₃
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In this equation, the 4 is a coefficient. These are whole numbers that multiply the following atom/molecule.
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In this equation, the 2 is a subscript. These are whole numbers that represent the number of atoms/molecules immediately proceeding it.
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soluble means dissolvable
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-some ionic salts will readily dissolve in water- these are soluble
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-when they dissolve the ions dissociate (break apart into their + and - ions)
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-other ionic salts will only sparingly dissolve in water- these are considered insoluble
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AB + CD --> AD + BC
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-a precipitate will only form if one of the products formed is insoluble
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-you will observe the solution becoming cloudy and typically white solids will form
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eg. lead nitrate + sodium carbonate --> lead carbonate + sodium nitrate
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colourless solution of lead nitrate mixed with colourless solution of sodium carbonate forms white precipitate of lead carbonate in a colourless solution of sodium nitrate.
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two soluble solutions were mixed together which allowed ions to exchange, forming the insoluble lead carbonation as a precipitate.
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lead carbonate is insoluble because lead ions and carbonate ions are more attracted to each other than they are to water.
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Metals
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silvery grey except copper which is pinky orange. Copper metal formed in a displacement reaction is reddy-brown.
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Gas
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oxygen, hydrogen, and carbon dioxide are all colourless.
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Carbonates
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white solids except copper carbonate which is a green solid and silver carbonate which is a yellow solid.
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Hydroxides
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white solids except iron (II) hydroxide which is a green solid, iron (III) hydroxide which is an orange/red solid, and copper hydroxide which is a blue solid.
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Hydrogen peroxide is a colourless liquid.
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Manganese dioxide is a black solid which catalyses the decomposition of hydrogen peroxide into water and oxygen gas.
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Combination Reaction Observations
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Magnesium burns with a bright light to form a grey-white ash of MgO.
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Sulfur; yellow non-metal- burns with a blue flame to form a colourless gas with a suffocating, choking odour, SO₂.
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Carbon; black non-metal- burns with a yellowy flame to make a colourless gas CO₂.
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Iron + Sulfur react when heated- glows and forms a black non-magnetic solid of FeS.
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Hydrogen; colourless gas + O₂ will explode with a small flame. After heating the solid glows a red-hot and a black solid is formed.
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Tests for Products Observations
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Hydrogen
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gas burns with a squeaky pop
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Carbon Dioxide
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gas turns colourless limewater cloudy/milky
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Oxygen
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gas relights a glowing splint
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Water
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turns blue cobolt chloride paper pink
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when a single atom 'displaces' another metal ion from within a compound.
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More reactive metals on the activity series replace a less reactive metal ion from the compound. Ag is the least reactive metal.
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metal A +compound BC --> compound AC +element B
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eg. Mg+FeSO₄-->Fe+MgSO₄ because magnesium is more reactive than iron
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To form an ionic equation, we get rid of the negative ion (spectator ion) because it is not involved in the reaction.
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eg. to form Mg + Fe2+ --> Fe + Mg2+*
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