Chemical changes

• What type of substance is copper oxide?

  Base
• What type of reaction occurs when copper oxide reacts with dilute hydrochloric acid?

  Neutralization reaction
• How can you produce pure dry crystals of copper chloride from copper oxide and dilute hydrochloric acid?

  React, filter, evaporate, and crystallize
• What is one variable the student should control in the metal reactivity investigation?

  Concentration of copper sulfate solution
• What is the independent variable in the investigation of metal reactivity?

  Type of metal
• What happens when zinc powder is added to copper sulfate solution?

  The solution decolorizes and red-brown powder forms
• How can the metals be ordered based on their reactivity from the temperature rise data?

  From highest to lowest temperature rise
• Why is it not possible to be certain about the order of reactivity based on the results?

  Results may vary due to experimental error
• Suggest one way to improve the investigation for more reliable results.

  Repeat the experiment multiple times
• Why can't copper chloride be produced by reacting copper with hydrochloric acid?

  Copper is less reactive than hydrogen
• What would you observe when magnesium reacts with water?

  Bubbles of hydrogen gas are produced
• What gas is produced at the anode during the electrolysis of copper(II) chloride?

  Chlorine gas
• What are two ways to increase the rate of reaction between calcium carbonate and hydrochloric acid?

  Increase temperature and concentration
• Explain why increasing the temperature increases the rate of reaction in terms of particles.

  Particles move faster and collide more often
• What is an exothermic reaction?

  Reaction that releases heat
• Sketch an energy profile diagram for an exothermic reaction.

  Diagram shows energy decrease with activation energy
• Why does the temperature of the solution increase during an exothermic reaction?

  Heat is released into the solution
• What do acids react with to produce a salt and water?

  Bases
• What is the word equation for hydrochloric acid and sodium hydroxide?

  Hydrochloric acid + Sodium hydroxide → Salt + Water
• What are the products of hydrochloric acid reacting with zinc?

  Zinc chloride and hydrogen gas
• Write a balanced symbol equation for the reaction of hydrochloric acid with zinc.

  $Zn +$$2HCl → ZnCl_2 +$$H_2$
• How can you test for hydrogen gas and what observation would you make?

  Use a lit splint; it makes a 'pop' sound
• Write a balanced symbol equation for magnesium reacting with dilute sulfuric acid, including state symbols.

  $Mg(s) +$$H_2SO_4(aq) → MgSO_4(aq) +$$H_2(g)$
• Why is the reaction between magnesium and sulfuric acid fast?

  Magnesium is highly reactive
• How would increasing the concentration of sulfuric acid affect the rate of reaction with magnesium?

  The rate of reaction would increase
• How can metals be arranged based on their reactivity?

  By their reactions with water and acids
• Order the following metals by reactivity: Magnesium, Copper, Zinc, Potassium.


  Potassium, Magnesium, Zinc, Copper
• Why does potassium react violently with water while copper does not?

  Potassium is highly reactive; copper is not
• Write a balanced symbol equation for the reaction of zinc with hydrochloric acid.

  $Zn +$$2HCl → ZnCl_2 +$$H_2$
• What is the name of the process of coating iron with zinc to prevent rusting?

  Galvanization
• How does zinc coating prevent rusting of iron?

  Zinc acts as a sacrificial anode
• What happens to iron when it rusts, including the chemical name of the product formed?

  Iron reacts with oxygen to form iron oxide
• What product is formed at the cathode during the electrolysis of molten sodium chloride?

  Sodium
• What product is formed at the anode during the electrolysis of molten sodium chloride?

  Chlorine
• Write the half-equation for the reaction at the cathode during electrolysis of sodium chloride.

  $Na^+$$+$$e^- → Na$
• Write the half-equation for the reaction at the anode during electrolysis of sodium chloride.

  $2Cl^- → Cl_2 +$$2e^-$
• Why is cryolite used in the electrolysis of aluminium oxide?

  It lowers the melting point of alumina
• Write the half-equation for the reaction at the cathode during the electrolysis of aluminium oxide.

  $Al^{3+} +$$3e^- → Al$
• Why is carbon dioxide produced during the electrolysis of aluminium oxide?

  Carbon anodes react with oxygen
• What is a suitable indicator for titration between sodium hydroxide and hydrochloric acid?

  Phenolphthalein