4.2 Reactions of Acids

• What do acids react with to produce a salt and hydrogen?

  Some metals
• What type of reactions occur when acids react with metals?

  Redox reactions
• How can you identify which substances are oxidized and reduced in a redox reaction?

  By looking at electrons gained and lost (following OIL RIG)
• What is the ionic equation for magnesium reacting with hydrochloric acid?

  Mg -> Mg$^{2+}$ + 2e$^{-}$
• What is the ionic equation for hydrogen in the reaction with hydrochloric acid?

  2H$^{+}$ + 2e$^{-}$ -> H$_{2}$
• What do acids produce when neutralized by alkalis and bases?

  Salts and water
• What is the general equation for the neutralization of acids by alkalis?

  Acid + alkali -> salt + water
• What do acids produce when neutralized by metal carbonates?

  Salts, water, and carbon dioxide
• What type of salt does hydrochloric acid produce?

  Chlorides
• What type of salt does nitric acid produce?

  Nitrates
• What type of salt does sulfuric acid produce?

  Sulfates
• What must the charges on the positive and negative ions from the acid and base add up to?

  Zero
• What is the salt produced when sodium hydroxide reacts with sulfuric acid?

  Na$_{2}$SO$_{4}$
• What can soluble salts be made from?

  Acids reacting with solid insoluble substances
• What is the process for making soluble salts from acids?

  1. Add chosen solid insoluble substance to the acid.
  2. Neutralization occurs when excess solid sinks to the bottom.
  3. Filter out excess solid, leaving the salt solution.
  4. Evaporate some water, then leave the rest to evaporate slowly (crystallisation).
• What do acids produce in aqueous solutions?

  H$^{+}$ ions
• What do alkalis produce in aqueous solutions?

  OH$^{-}$ ions
• What does the pH scale measure?

  The acidity or alkalinity of a solution
• What is the pH of a neutral solution?

  7
• What does a pH less than 7 indicate?

  The solution is acidic
• What does a pH greater than 7 indicate?

  The solution is alkaline
• What is the ionic equation for any neutralization reaction?

  H$^{+}$(aq) + OH$^{-}$(aq) -> H$_{2}$O(l)
• What is the purpose of titration in chemistry?

  To measure the volumes of acid and alkali solutions that react with each other
• What are the steps to carry out a titration?

  1. Wash burette with dilute hydrochloric acid and water.
  2. Fill burette to 100cm³ with acid.
  3. Use a 25cm³ pipette to add alkali to a conical flask.
  4. Add a few drops of a suitable indicator.
  5. Add acid from burette to alkali until the end-point is reached.
  6. Calculate the titre (volume of acid needed).
  7. Repeat for precise results.
• How many cm³ are in 1 dm³?

  1000 cm³
• What is the relationship between moles and grams for a substance?

  One mole of a substance in grams is the same as its relative atomic mass in grams
• How do you calculate the concentration of hydrochloric acid in the given example?

  0.4 mol/dm³
• What characterizes a strong acid in aqueous solution?

  It is completely ionized
• What characterizes a weak acid in aqueous solution?

  It is partially ionized
• How does the strength of an acid relate to its pH?

  A stronger acid has a lower pH
• What happens to the H$^{+}$ concentration as the pH decreases by one unit?


  It increases by a factor of 10
• What is the difference between strong/weak acids and concentrated/dilute acids?

  Strong/weak refers to ionization, while concentrated/dilute refers to the amount of substance in a given volume
• What are examples of strong and weak acids?

  • Strong acids: Hydrochloric, nitric, sulfuric acids
  • Weak acids: Ethanoic, citric, carbonic acids