C4 - Chemical Changes

• What type of reaction is metal + oxygen -> metal oxide?

  Oxidation reaction
• What is the reactivity series?

  Order of metals by reactivity
• Why are potassium, sodium, and lithium at the top of the reactivity series?

  They are very reactive with cold water
• Why are calcium, magnesium, and iron in the middle of the reactivity series?

  They react with dilute hydrochloric acid
• What are copper, silver, and gold at the base of the reactivity series?

  They don't react with water or acids
• What do metals form when they react?

  Positive ions
• What is meant by a displacement reaction?

  More reactive metal displaces less reactive one
• Give an example of a displacement reaction.

  Sodium zinc chloride → sodium chloride + zinc
• How is gold extracted?

  Found as itself in the earth
• What is reduction?

  The loss of oxygen
• What is produced when metals react with acids?

  A salt and hydrogen gas
• How are metals less reactive than carbon extracted?

  Heated with carbon from their oxides
• In terms of electrons, what is oxidation?

  The loss of electrons
• In terms of electrons, what is reduction?

  The gain of electrons
• Give an example of a metal reacting with an acid.

  Magnesium + sulfuric acid → magnesium sulfate + hydrogen
• When metals react with acids, what is oxidized and reduced?

  The metal is oxidized, hydrogen ions are reduced
• Why are the reactions of metals with acids called redox reactions?

  They involve oxidation and reduction
• What is the difference between a base and an alkali?

  A base is insoluble; an alkali is soluble
• By what three types of substances can acids be neutralized?

  By bases, alkalis, or metal carbonates
• Give the two ionic half equations for when magnesium reacts with hydrochloric acid.

  Mg (s) → Mg²⁺(aq) + 2e⁻ and 2H⁺(aq) + 2e⁻ → H₂ (g)
• What are the products when copper carbonate reacts with hydrochloric acid?

  Copper chloride + water + CO₂
• What are the products of neutralization reactions?

  Salt plus water, CO₂ with carbonates
• What are the products when zinc oxide reacts with nitric acid?

  Zinc nitrate + water
• What are the products when calcium hydroxide reacts with sulfuric acid?

  Calcium sulfate + water
• How can soluble salts be produced from acids?

  By reacting with solid insoluble substances
• Describe the method for producing soluble salts from acids.

  Add solid to acid until no more reacts
• How can solid salts be made from the salt solutions?

  By crystallizing from the solutions
• What is an acid?

  Forms hydrogen ions in aqueous solution
• What is an alkali?

  Forms hydroxide ions in aqueous solution
• What does the pH scale (0-14) measure?

  The acidity or alkalinity of a solution
• How can pH be measured?

  Using universal indicator or a pH probe
• What do pHs of 7, below 7, or above 7 indicate?

  7 is neutral; below is acidic; above is alkaline
• Why do neutralization reactions always produce water?

  H⁺ ions react with OH⁻ ions to form water
• What is the difference between a strong and a weak acid?

  Strong acids completely ionize; weak acids partially ionize
• Give examples of strong acids.

  Hydrochloric, sulfuric, nitric acid
• Give examples of weak acids.

  Ethanoic, citric, carbonic acid
• How does acid strength affect pH?

  Stronger acids have lower pH for concentration
• What happens to the H⁺ concentration as pH decreases by one unit?

  Increases by a factor of 10
• What is an electrolyte?

  A molten ionic substance that conducts electricity
• What happens to ionic compounds when they are melted or dissolved in water?

  The ions are free to move