[Part 3]- C6- electrolysis💧

• aqueous solutions are dissolved in water- meaning they form when substances are dissolved in water • and water molecules ionise/dissociate [split], forming hydrogen ion and hydroxide ions.

• copper sulfate solution, has the formula CuSO4 (aq)- containing the copper ion: CU^2+ and the sulfate ion: SO4^2- • because it’s dissolved in water, the hydrogen ion H^+ and the hydroxide ion OH^- needs to be considered.

• the copper sulfate solution, contains two positive ions that would be attracted to the cathode. • ; the rule, is that hydrogen is (only) produced at the cathode, if the metal is more reactive than hydrogen. • and because copper is less reactive than hydrogen, copper will be produced at the cathode.

• and at the anode, oxygen gas is made- [because oxygen is usually produced at the anode, when aqueous solutions are electrolysed]

• the electrodes are inert [unreactive] because, it’s important that the electrodes don’t react, with the chemicals that are being made in electrolysis. • otherwise, the electrodes will take part in the reaction

• Cu^2+ 2e^- ————-> Cu • this is a reduction reaction, as the copper ions are gaining electrons, to form copper atoms.

4OH^- ———> O2 + 2H2O + 4e^- OR 4OH^- ➖ 4e^- ———-> O2 + 2H2O • four hydroxide ions react to form oxygen gas and water, using a total of four electrons in the process- therefore this is an oxidation reaction.

• ; the rule, is that hydrogen is (only) produced at the cathode, if the metal is more reactive than hydrogen.

• sodium chloride solution, has the formula: NaCl^- containing the sodium ion: Na and the chloride ion Cl^- • because it’s dissolved in water, the hydrogen ion H^+ and the hydroxide ion OH^- needs to be considered.

• the sodium chloride solution, contains two positive ions that would be attracted to the cathode. [the sodium ion Na^+ and the hydroxide ion H^+] • ; the rule, is that hydrogen is (only) produced at the cathode, if the metal is more reactive than hydrogen. • and because sodium is more reactive than hydrogen, hydrogen gas will be produced at the cathode.

• and at the anode, there are two negative ions that could be attracted to it- [the chloride ion: Cl^- and the hydroxide ion OH^-] • ; the rule for the anode is: that if the aqueous solution contains halide ions, then halogen will be produced at the anode. [otherwise it would typically be oxygen gas] • therefore at the anode, chlorine gas is made- since the sodium chloride solutions, contains a halide ion [chloride]

• H^+ ➕ e^- ———> H • this is a reduction reaction, as the hydrogen ion is gaining one electron, to form a hydrogen atom.

• Since hydrogen atoms immediately pair up to form a hydrogen molecule [H2]- as hydrogen is a diatomic molecule, the half equation is doubled and now looks like this: • 2H^+ ➕ 2e^- ———> H2

• Cl^- ———-> Cl + e^- • ; as chloride atoms always pair to form a double molecule, the half-equation must be doubled: • 2Cl^- ———-> Cl2 + 2e^- OR • 2Cl^- ➖ 2e^- ———-> Cl2 • this is an oxidation reaction, as chlorine loses one electron, to form a chlorine atom.

• the rule for the anode is: that if the aqueous solution contains halide ions, then halogen will be produced at the anode. • [otherwise it would typically be oxygen gas, as the hydroxide ions would be attracted to the anode] • these halides ions are: fluoride (F −), chloride ( Cl −), bromide ( Br −), iodide ( I −) and astatide ( At −)

• fluoride (F −) • chloride ( Cl −) • bromide ( Br −) • iodide ( I −) • astatide ( At −)

• NaCl [aq] ——-> NaOH [aq]

• During the electrolysis of brine, hydrogen and chloride ions are removed from sodium chloride solution solution . • ; sodium and hydroxide ions are left behind in solution. • This means that sodium hydroxide is also formed during the electrolysis of sodium chloride solution.

• Because hydrogen and chloride ions are removed from sodium chloride solution • and sodium hydroxide is also formed, during the electrolysis of sodium chloride solution. [because sodium and hydroxide ions are left behind in solution.] • the products of electrolysis of brine can be used

• hydrogen can be used for fuel cells and rockets • chlorine can be used for bleach and swimming pools • and sodium hydroxide can be used for: making soap, and unblocking drains.

• Brine is a solution of sodium chloride (NaCl) and water (H2O)

Water (l) electicity ⟶ Hydrogen (g)+ Oxygen (g)

• litmus paper will turn blue at the anode

• when writing half -equations, if there is a positively charged ion, the electron goes before the arrow to balance the charges