Chemistry

• Hydrochloric Acid

  HCl
• (aq)

  aqueous solution
• Aqueous solution

  Dissolved in water
• Sulfuric Acid


  H2SO4
• Nitric Acid


  HNO3
• In aqueous solutions, acids produce hydrogen ions (H+)
• Hydrochloric Acid in aqueous solution

  HCl(aq) -> H+(aq) + Cl-(aq)
• Bases are chemicals that can neutralise acids producing a salt and water.
• Bases are usually metal oxides and metal hydroxides.
• Bases which are soluble in water are called alkalis.
• In aqueous solution, alkalis produce hydroxide ions (OH-).
• The pH scale shows us the acidity or the alkalinity of a solution.
• Acids have a pH between 0 and 6.
• Alkalis have a pH between 8 and 14.
• Water/Neutral solutions have a pH of 7.
• A pH probe determines the pH electronically.
• The pH of a solution can be determined by a pH probe or by comparing the colour on the universal indicator paper to the colours on a pH colour chart.
• Universal indicator paper changes colour depending on whether the solution is acidic, neutral or alkaline.
• Green shows a neutral solution (7).
• Very acidic solutions show a very red colour (0).
• A purple colour shows a very alkaline solution (14).
• Neutralisation reaction

  H+(aq) + OH-(aq) -> H2O
• Neutralisation reaction word equation

  hydrogen ion + hydroxide ion -> water
• The pH scale measures how acidic or alkaline a substance is.
• Water has a pH value of 7, which is considered to be neutral.
• Acidic substances have low pH values, while alkaline substances have high pH values.
• Soluble bases or alkalis react with acids to form a salt and water only. The type of reaction involved is neutralisation.
• Titration is a technique used to work out the concentration of an unknown solution when you know the concentration of another solution.
• A student investigated the reactions of copper oxide with dilute sulfuric acid. In the reaction one of the products is copper sulfate. Describe how a sample of pure, dry copper sulfate crystals could be made from copper oxide and dilute sulfuric acid. Write word equation for reaction. (1/2)


  1. Wear safety goggles and stay away from flame.
  2. Mix copper oxide with dilute sulfuric acid in a beaker.
  3. Filter the mixture using filter paper into a measuring tube.
• Magnesium carbonate, MgCO3, can be reacted with dilute sulfuric acid to form magnesium sulfate (MgSO4), water and another product. Write the balanced symbol equation for this reaction.

  MgCO3 + H2SO4 -> MgSO4 + H2O + CO2
• A student investigated the reactions of copper oxide with dilute sulfuric acid. In the reaction one of the products is copper sulfate. Describe how a sample of pure, dry copper sulfate crystals could be made from copper oxide and dilute sulfuric acid. Write word equation for reaction. (2/2)

  4. Heat the filtered solution gently to evaporate some water and concentrate it.

  5. Allow it to cool for crystals to form.

  6. Collect the crystals and place them on filter paper to dry.

  7. Copper oxide + Sulfuric acid -> Copper sulfate + water
• Explain, in terms of the particles present, why the pH increases during neutralisation.

  The pH increases during neutralisation because at the start of the experiment, there are lots of H+ ions, but as we add the alkali the amount of H+ ions decreases and the amount of OH- ions increase because it becomes less acidic as it forms water, which is neutral.
• Metal oxides react with acids to form a salt and another product. Complete the word equation for the reaction of magnesium oxide with nitric acid.

  magnesium oxide + nitric acid -> magnesium nitrate + water
• Dilute hydrochloric acid is a strong acid.

  Explain why dilute hydrochloric acid is described as a strong acid

  Dilute hydrochloric acid is a strong acid because it has fully dissociated H+ ions.
• What is the colour of phenolphthalein in a solution of ethanoic acid?

  Colourless
• What colour is seen when methyl orange is added to an alkaline solution?

  Yellow
• soluble/insoluble = The ability of a substance to dissolve into a liquid.
• Solubility = describes how much of a substance can dissolve in a solvent
• solvent = substance that dissolves a solute to form a solution
• solution = homogenous mixture composed of 2 or more substances