Chemical Changes

• What is electrolysis?


  The process of breaking down ionic compounds into their elements using electricity.
• What is an electrolyte?

  A substance that conducts electricity when molten or dissolved in water, allowing electrolysis to occur.
• What are electrodes?


  Conductors (usually made of graphite or metal) that carry electricity into and out of the electrolyte during electrolysis.
• What is the anode?

  The **positive electrode** where **oxidation** occurs (loss of electrons).
• What is the cathode?

  The **negative electrode** where **reduction** occurs (gain of electrons).
• What happens to positive ions (cations) during electrolysis?

  They move to the **cathode** and gain electrons (are reduced).
• What happens to negative ions (anions) during electrolysis?

  They move to the **anode** and lose electrons (are oxidized).
• What is produced at the cathode during the electrolysis of molten lead(II) bromide ($PbBr_2$)?


  **Lead metal** ($Pb$) is produced.
• What is produced at the anode during the electrolysis of molten lead(II) bromide ($PbBr_2$)?


  Bromine gas ($Br_2$) is produced.
• What is produced at the cathode during the electrolysis of aqueous sodium chloride ($NaCl$)?


  **Hydrogen gas** ($H_2$) is produced if the metal is more reactive than hydrogen.
• What is produced at the anode during the electrolysis of aqueous sodium chloride ($NaCl$)?


  **Chlorine gas** ($Cl_2$) is produced.
• What is the rule for predicting products at the cathode in aqueous solutions?

  If the metal is **more reactive than hydrogen**, hydrogen gas is produced. If the metal is less reactive, the metal is produced.
• What is the rule for predicting products at the anode in aqueous solutions?

  If halide ions (e.g., $Cl^-$, $Br^-$) are present, the **halogen** is produced. Otherwise, **oxygen gas** ($O_2$) is produced.
• What is the half-equation for the reduction of $Cu^{2+}$ ions at the cathode?


  $Cu^{2+} +$$2e^- \rightarrow Cu$
• What is the half-equation for the oxidation of $Cl^-$ ions at the anode?


  $2Cl^- \rightarrow Cl_2 +$$2e^-$
• What is the purpose of the diaphragm in the chlor-alkali industry?

  To separate the products (chlorine gas, hydrogen gas, and sodium hydroxide) to prevent them from reacting.
• What are the three main products of the chlor-alkali process?

  1. **Chlorine gas** ($Cl_2$)
  2. **Hydrogen gas** ($H_2$)
  3. **Sodium hydroxide** ($NaOH$)
• What is electroplating?


  The process of coating a metal object with a thin layer of another metal using electrolysis.
• Why is cryolite added during the electrolysis of aluminium oxide?

  To lower the melting point of aluminium oxide, reducing energy costs.
• What is the overall equation for the electrolysis of aluminium oxide ($Al_2O_3$)?


  $2Al_2O_3 \rightarrow 4Al +$$3O_2$
• What is the environmental impact of electrolysis?

  It can be energy-intensive, leading to high carbon emissions if the electricity comes from non-renewable sources.
• What is the pH of acids?

  Less than 7
• What taste do acids have?

  Sour taste
• What happens when acids react with metals?

  They produce hydrogen gas
• What do acids form when they react with bases?

  Salt and water
• What do acids release when they react with carbonates?

  Carbon dioxide
• What is a key property of acids?

  Corrosive
• What are the types of reactions acids undergo?

  • With metals: Produce hydrogen gas
  • With bases: Form salt and water
  • With carbonates: Release carbon dioxide
• What occurs during the reaction of zinc with dilute sulfuric acid?

  Hydrogen gas bubbles appear
• What is produced when magnesium reacts with hydrochloric acid?

  Hydrogen gas and magnesium chloride
• What is the general equation for neutralization reactions?

  $ACID +$$BASE \rightarrow SALT +$$WATER$
• What do acids release in water?

  Hydrogen ions (H⁺)
• What do bases release in water?

  Hydroxide ions (OH⁻)
• What is formed when hydrochloric acid reacts with sodium hydroxide?

  Sodium chloride and water
• What are the products of the reaction between sulfuric acid and potassium hydroxide?

  Potassium sulfate and water
• What do acids and carbonates produce in their reaction?

  A salt, water, and carbon dioxide
• What happens when hydrochloric acid reacts with calcium carbonate?

  It produces calcium chloride, water, and carbon dioxide
• What is released as bubbles when an acid is added to a carbonate?

  Carbon dioxide
• What is the reaction equation for hydrochloric acid and calcium carbonate?

  $2HCl +$$CaCO_{3} \rightarrow CaCl_{2} +$$H_{2}O +$$CO_{2}$
• What is a common observation when vinegar reacts with limestone?

  Bubbles of carbon dioxide are released