Science chapter 2 flashcard alkalis and salts

• What are bases used to make?

  Soap and paper
• What are alkalis?

  Bases which dissolve in water are called alkalis.
• Give me 5 examples of common alkalis.

  Limewater, Soap solution, Ammonia solution, Sodium hydroxide, Potassium hydroxide, Calcium hydroxide.
• What happens to alkalis when they dissolve in water?

  Alkalis ionise when they dissolve in water.
• (Alkalis ionise when they dissolve in water.)

  What is the ionic equation for the above process?

  NaOH → Na+ + OH-

  KOH → K+ + OH-
• What is alkali?

  Compounds that ionise to produce hydroxide ions(OH-)as the only negative ions.
• (When an alkali dissolves in water, ionization takes place when the water molecules reduce the force of attraction between the ions so that they become free moving ions.)

  What is the chemical equation for the above information?

  Ca(OH)2 → Ca2+ + 2OH-
• What are some common properties of alkalis?

  1. Alkalis can turn purple litmus solution blue.
  2. Alkalis can turn colourless phenolphthalein red.
  3. Alkalis react with acids to produce salts and water.
  4. Alkalis react with some non-metals oxides to produce salt and water.
  5. Alkalis react with some salts to form new salts and new bases
• What does water gases released from factories contain?

  Sulphur dioxide
• What do sulphur dioxide do?

  Pollutes the environment
• (Sodium hydroxide can react with some non-metals oxides(sulphur dioxide) to produce salt (sodium sulphite) and water.)

  What is the chemical equation for the above reaction?

  SO2 + 2NaOH → Na2SO3 + H2O
• (When carbon dioxide is passed into an aqueous solution of sodium hydroxide, sodium carbonate and water are produced.)

  What is the chemical formula for the above reaction?

  CO2 + 2NaOH → Na2CO3 + H2O
• Sodium hydroxide can also react with some salt to form new salts and new bases.
• (Sodium hydroxide reacts with copper (II) chloride to produce a new base, copper (II) hydroxide and a new salt, sodium chloride.)

  What is the chemical formulas for the above reaction?

  CuCl2 + 2NaOH → Cu(OH)2 ↓ + 2NaCl
• (Sodium hydroxide reacts with iron (III) chloride to produce a new base, iron (III) hydroxide and a new salt, sodium chloride.)

  What is the chemical formulas for the above reaction?

  FeCl3 + 3 NaOH → Fe(OH)3↓ + 3NaCl
• What is another name for Sodium hydroxide?

  Caustic soda
• It is very corrosive to our skin, paper, clothes etc.
• Sodium hydroxide is deliquescent. When exposed to air, sodium hydroxide absorbs water vapour easily from the air and becomes wet.
• What can sodium hydroxide be used as?

  Drying agent for some gases such as oxygen and hydrogen.
• What happens to sodium hydroxide dissolves in water easily?


  A lot of heat is given out.
• An aqueous solution of sodium hydroxide is bitter and slipery.
• Sodium hydroxide can also react with carbon dioxide in the air.
• What are some uses of sodium hydroxide?

  Sodium hydroxide is used in making soap and paper.
• What is calcium hydroxide commonly known as ?

  Slakedlime
• What is calcium hydroxide?

  A white powder
• Calcium hydroxide is sparingly soluble in water.
• What is limewater?

  A clear, aqueous solution of calcium hydroxide is called limewater.
• Calcium hydroxide is also corrosive.
• Why is calcium hydroxide not as dangerous as sodium hydroxide?

  Because it is less soluble in water.
• When exposed to air, calcium hydroxide can react with carbon dioxide, sulphur dioxide etc.
• (Calcium hydroxide solution react with sodium carbonate solution to form calcium carbonate and sodium hydroxide. ) What is the chemical formulae for the above reaction?

  Ca(OH)2 + Na2CO3 → CaCO3↓ + 2NaOH
• Calcium carbonate is insoluble in water and can be obtained by filtration.
• How is solid sodium hydroxide obtained?

  By using the evaporation method.
• Evaporation method is used to prepare a small amount of sodium hydroxide in the industry.
• What are some uses of calcium hydroxide?

  Reducing PH of soil

  Painting

  Softening hard water

  Construction
• Gastric juice in our stomach contains hydrochloric acid
• What is the uses of hydrochloric acid?

  Helps in digestion

  Kills germs that enter the human body.
• How is excess acid in the stomach neutralized?

  By taking medicine containing aluminium hydroxide.
• What is pH values?

  pH values represent the acidity or alkalinity of a solution.
• pH values are related to the concentrations of hydrogen ions(H+) and hydroxide ions (OH-).