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Chemistry (Chemical changes (Reactions of acids, Electrolysis (Explain how…

- - - - Calcium
        
        Dilute Acids - Calcium reacts with dilute hydrochloric acid to give calcium chloride and hydrogen gas. Calcium reacts with dilute sulphuric acid to give calcium sulfate and hydrogen gas. The initial reaction is fast, but gradually slows down.
        
        WATER - Calcium reacts slowly with water. The reaction forms calcium hydroxide, Ca(OH)2 and hydrogen gas (H2).
      - Magnesium
        
        Dilute Acids - The products of acid/metal reactions are a salt and hydrogen gas.
        
        WATER - Magnesium metal does however react with steam to give magnesium oxide (MgO) (or magnesium hydroxide, Mg(OH)2, with excess steam) and hydrogen gas (H2).
      - Zinc
        
        Dilute Acids - The products of acid/metal reactions are a salt and hydrogen gas.
        
        WATER - Zinc virtually has no reaction with cold water.
      - Iron
        
        WATER - Air-free water has little effect upon iron metal.
        
        Dilute Acids - The products of acid/metal reactions are a salt and hydrogen gas.
      - Lithium
        
        Dilute Acids - Lithium reacts with dilute hydrochloric acid to give Lithium chloride and hydrogen gas. Lithium reacts with dilute sulphuric acid to give Lithium sulphate and hydrogen gas. Lithium may react with dilute acids explosively
        
        WATER - When lithium is added to water, lithium floats. It fizzes steadily and becomes smaller, until it eventually disappears.
      - Sodium
        
        Dilute Acids - Sodium reacts with dilute hydrochloric acid to give sodium chloride and hydrogen gas. Sodium reacts with dilute sulphuric acid to give sodium sulphate and hydrogen gas. Sodium may react with dilute acids explosively
        
        WATER - When sodium is added to water, the sodium melts to form a ball that moves around on the surface. It fizzes rapidly, and the hydrogen produced may burn with an orange flame before the sodium disappears.
      - Pottassium
        
        Dilute Acids - Potassium reacts with dilute hydrochloric acid to give potassium chloride and hydrogen gas. Potassium reacts with dilute sulphuric acid to give potassium sulphate and hydrogen gas. Potassium reacts with dilute acids explosively
        
        WATER - When potassium is added to water, the metal melts and floats. It moves around very quickly on the surface of the water. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame. There is sometimes a small explosion at the end of the reaction.
      - Copper
        
        WATER -Copper does not react with water
        
        Dilute Acids - Copper is below hydrogen in the electrochemical series and thus does not react with acids to liberate hydrogen
    - - A native metal is any metal that is found in its metallic form, either pure or as an alloy, in nature. Gold is a native metal as it is not found as a compound
    - - Oxidation is the gain of oxygen by a substance.
        
        magnesium + oxygen → magnesium oxide
        2Mg + O2→ 2MgO
      - Reduction is the loss of oxygen from a substance
        
        copper oxide + hydrogen → copper + water
        CuO + H2→ Cu + H2O
    - - extract by reaction with carbon or carbon monoxide:
        zinc
        iron
        tin
        lead
      - extracted in various ways:
        copper
        silver
        gold
        platinum
      - extract by electrolysis:
        potassium
        sodium
        calcium
        magnesium
        aluminium
      - The method of extraction of a metal from its ore depends on the metal's position in the reactivity series.
  - - - Electrons are shown as e- in half-equations. A half-equation is balanced by adding, or taking away, a number of electrons equal to the total number of charges on the ions in the equation.
      - Write the formulae of the reactant and product. Cl- → Cl2
        
        Adjust the number of ions, if needed. 2Cl- → Cl2
        
        Count the number of charges. Add enough electrons so that both sides have the same total number of charges. 2Cl- → Cl2 2e-
    - - OILRIG
    - - By evaporating the solution
    - - Base - Any of a class of compounds that form hydroxyl ions (OH) when dissolved in water, and whose aqueous solutions react with acids to form salts.
    - - make (a liquid) thinner or weaker by adding water or another solvent to it.
      - Concentrated = high proportion relative to other substances
  - - - -the metal will be produced if it is less reactive than hydrogen
        -hydrogen will be produced if the metal is more reactive than hydrogen
      - So, for example, the electrolysis of copper chloride solution produces copper at the negative electrode. However, the electrolysis of sodium chloride solution produces hydrogen.
    - - -the metal is formed at the negative electrode because that is where the positive metal ions are attracted
        -the non-metal element is formed at the positive electrode where the negative non-metal ions are attracted
    - - Electrolysing aqueous solutions of ionic compounds can be more complicated than electrolysing molten compounds, because the water molecules can provide hydrogen ions (H+) and hydroxide ions (OH-), in addition to the ions from the ionic compounds.
    - - This is what happens during electrolysis:
        -Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.
        -Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised. The substance that is broken down is called the electrolyte.
    - - A half-equation shows you what happens at one of the electrodes during electrolysis. Electrons are shown as e-. A half-equation is balanced by adding, or taking away, a number of electrons equal to the total number of charges on the ions in the equation.
      - When positive metal ions (cations) arrive at the negative electrode (the cathode), they gain electrons to form neutral metal atoms. This is called reduction. For example:
        Pb2+ + 2e- → Pb
      - When negative non-metal ions (anions) arrive at the positive electrode (the anode), they lose electrons to form neutral atoms or molecules. This is called oxidation. For example:
        2Br- → Br2 + 2e-
    - - The ions must be free to move, which is possible when an ionic substance is dissolved in water or it is melted.
      - electrolyte - a liquid or gel which contains ions and can be decomposed by electrolysis, e.g. that present in a battery.
- - - - https://vceasy.files.wordpress.com/2014/02/1-1-2a1.png
    - - Unlike the plum pudding model, where those atoms simply floated in "soup," Rutherford believed they orbited the central nucleus just as planets orbit the sun.
    - - Separating solids from liquids – evaporation
      - Separating the solvent from a solution – simple distillation
      - Separating solids from liquids – filtration
      - Separating dissolved solids – chromatography
    - - Proton—positive; electron—negative; neutron—no charge
    - - A mixture is made from different substances that are not chemically joined.
    - - Neutrons are neutral, but protons and electrons are electrically charged. Protons have a relative charge of +1, while electrons have a relative charge of -1.
    - - copper sulfate + sodium hydroxide → sodium sulfate + copper hydroxide
        CuSO4(aq) + 2NaOH(aq) → Na2SO4(aq) + Cu(OH)2(s)
      - 2Cl- – 2e– → Cl2
    - - Atomic mass - atomic no. = neutrons
    - - Word equation: copper + oxygen → copper oxide
      - Symbol equation: 2Cu + O₂ → 2CuO
    - - Isotopes are atoms of an element with the normal number of protons and electrons, but different numbers of neutrons. Isotopes have the same atomic number, but different mass numbers.
    - - The relative atomic mass is a measure of the mass of one atom of the element.
      - The relative atomic mass of an element (Ar) is an average value for the isotopes of the element. For example, the Ar for chlorine is 35.5 because it contains two different isotopes.
    - - All matter is made of atoms. There are over a hundred different types of atom, called elements, and each one has a symbol. The atoms of a particular element are identical to each other.
      - When atoms of different elements join together they make a compound. Compounds are represented by formulae that show how many atoms of each element are in the compound. Formulae can be worked out from the charge of the ions that make up the compound.
    - - Chlorine's Ar of 35.5 is an average of the masses of the different isotopes of chlorine. This is calculated by working out the relative abundance of each isotope. For example, in any sample of Chlorine 25% will be 37Cl and 75% 35Cl. The relative atomic mass is therefore calculated using the equation:
        (% of isotope 1 × mass of isotope 1) + (% of isotope 2 × mass of isotope 2) ÷ 100
        So in the case of chlorine:
        (75 × 35) + (25 × 37)∕100
        = 2625 + 925∕100
        = 35.3
    - - the nucleus is shown as a black spot
        each energy level is shown as a circle around the nucleus
        each electron is shown by a dot or a cross.
      - each energy level is a new number e.g. 2(1st shell), 8(2nd shell), 4(3rd shell)
  - - - As they already have a full outer shell, they do not want to loose or gain any electrons.
    - - Typical nonmetals have a dull, coloured or colourless appearance; are brittle when solid; are poor conductors of heat and electricity; and have acidic oxides
    - - The noble gases have the following properties in common:
        they are non-metals
        they are very unreactive gases
        they are colourless
        they exist as single atoms (they are monatomic)
    - - Mendeleev also arranged the elements known at the time in order of relative atomic mass, but he did some other things that made his table much more successful.
        He realised that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table.
    - - As you go down Group 1 the atoms become larger and the outer electron is further from the nucleus. The force of attraction between the positively-charged nucleus and the negatively-charged outer electron becomes weaker, which is why the outer electron is more easily lost.
        So potassium is more reactive than lithium because the outer electron of a potassium atom is further from its nucleus than the outer electron of a lithium atom.
    - - An English scientist called John Newlands put forward his Law of Octaves in 1864. He arranged all the elements known at the time into a table in order of relative atomic mass.
    - - halogens - get less reactive as you go down the group.
      - The halogens become darker as you go down the group. Fluorine is very pale yellow, chlorine is yellow-green, and bromine is red-brown. Iodine crystals are shiny purple - but easily turn into a dark purple vapour when they are warmed up.
    - - For metals, reactivity increases down a group and from right to left across a period. Nonmetals do the opposite. For nonmetals, reactivity increases up a group and from left to right across a period. Francium is the most reactive metal, and fluorine is the most reactive nonmetal.
    - - The halogens react with metals to make salts called metal halides.
      - When reacting with hydrogen and other non-metals, the halogen atoms share electrons, forming molecules with covalent bonds. Halogens can also form covalent bonds with each other to give diatomic atoms.
    - - Elements with similar chemical properties are in the same group of elements.
    - - Elements are arranged in order of increasing atomic number.
- - - - Ionic bonds are the electrostatic forces of attraction between oppositely charged ions.
    - - Ions are electrically charged particles formed when atoms lose or gain electrons. This loss or gain leaves a complete highest energy level, so the electronic structure of an ion is the same as that of a noble gas - such as a helium, neon or argon.
      - There is a quick way to work out what the charge on an ion should be:
        The number of charges on an ion formed by a metal is equal to the group number of the metal
        The number of charges on an ion formed by a non-metal is equal to the group number minus eight
        Hydrogen forms H+ ions.
    - - Ionic bonding is the electrostatic force of attraction between positively and negatively charged ions.
        These ions have been produced as a result of a transfer of electrons between two atoms with a large difference in electronegativities.
        Ionic bonding results from metals combining with non-metals. For example, sodium (a metal) combining with chlorine (a non-metal).
      - Metallic bonding is the strong attraction between closely packed positive metal ions and a 'sea' of delocalised electrons.
      - Atoms in a covalent bond are held together by electrostatic forces of attraction between positively charged nuclei and negatively charged shared electrons.
  - - - Ionic substances form giant ionic lattices containing oppositely charged ions. They have high melting and boiling points, and conduct electricity when melted or dissolved in water.
      - High melting and boiling points - Ionic bonds are very strong - a lot of energy is needed to break them. So ionic compounds have high melting and boiling points.
        Conductive when liquid - Ions are charged particles, but ionic compounds can only conduct electricity if their ions are free to move. Ionic compounds do not conduct electricity when they are solid - only when dissolved in water or melted.
    - - Solid (s), liquid (l), gas (g), or dissolved in water (aq).
- - - - The relative atomic mass of an element shows its mass compared with the mass of atoms of other elements.
    - - before formula in normal script - the amount of each.
      - subscript - two atoms of the element it is after
    - - Every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. Therefore, there must be the same number of atoms of each element on each side of a chemical equation.
  - - - One mole of a substance is its gram formula mass (GFM)
      - How many molecules are contained in 0.65 mole of sulphur dioxide, SO2?
        Answer
        Find: m molecules from 0.65 mole of SO2
        Link: 6.02 × 1023 formula units ↔ 1 mole
        Convert: 6.02 × 1023 molecules ↔ 1 mole
        Proportion: There are 6.02 × 1023 molecules in 1 mole. Hence, in 0.65 mole:
        m = 0.65 × (6.02 × 1023)
        m = 3.91 × 1023
        Answer: 3.91 x 1023 molecules are in 0.65 mole of SO2.
- - - - The rate of reaction
    - - For a chemical reaction to occur, the reactant particles must collide. But collisions with too little energy do not produce a reaction.
      - the energy curve goes up from the reactants’ energy level to begin with, then drops to the products’ energy level. This is because many reactions need an input of energy to start the reaction off. This is energy is called the activation energy. It is represented on an energy level diagram as the difference between the reactants’ energy level and the top of the curve.
    - - Combustion (burning). Many oxidation reactions, for example rusting
      - Electrolysis
        The reaction between ethanoic acid and sodium carbonate
        The thermal decomposition of calcium carbonate in a blast furnace
    - - Exothermic reactions
        These are reactions that transfer energy to the surroundings. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to become hotter.
        Endothermic reactions
        These are reactions that take in energy from the surroundings. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to get colder. The temperature decrease can also be detected using a thermometer.
    - - Bond-breaking is an endothermic process. Energy is released when new bonds form. Bond-making is an exothermic process.
      - You can calculate the energy change in a reaction using bond energies. A bond energy is the amount of energy needed to break a mole of a particular bond. You will be given any bond energies you need in the exam.
        Method
        Add together all the bond energies for all the bonds in the reactants – this is the ‘energy in’.
        Add together the bond energies for all the bonds in the products – this is the ‘energy out’.
        Calculate the energy change: energy in – energy out.