Acids & Alkalis ⚗️

• What do the main hazard symbols mean?

  Warning symbols used to alert individuals to the presence of a hazardous material or situation.

  
• What are the safety precautions that should be taken when handling different acids or alkalis?

  -Gloves should be worn to ensure they don't irritate or burn the skin.

  -wear goggles so the acid or alkali doesn't get in the eyes and burn or irritate them.
• What ions are present in all acidic solutions?

  Hydrogen ions.
• What ions are present in all alkaline solutions?

  Hydroxide ions.
• What pH values do acidic solutions have?

  pH 1,2,3,4,5,6.
• What pH value do neutral solutions have?

  7.
• What pH values do alkaline solutions have?

  pH 8,9,10,11,12,13,14.
• What is the effect of acids on common indicators?

  Litmus - paper turns red if it's an acid.

  Universal - change in colour to red (strong acid) or yellow (weak acid).
• What is the effect of alkalis on common indicators?

  Litmus - paper turns blue if it's an alkali.

  Universal - change in colour to blue (weak alkali) and purple (strong alkali).
• How does pH link to the concentration of ions in an acid?

  The more hydrogen ions there are, the higher their concentration so the more acidic the solution is and the lower it's pH.
• How does pH link to the concentration of ions in an alkali?

  The higher the number of hydroxide ions, the higher the concentration so the more alkaline the solution is and the higher its pH.
• What is the difference between a dilute and concentrated solution?

  A concentrated solution contains more dissolved solute than a dilute solution.
• Explain the difference between strong and weak acids (in terms of disassociation of the acid molecules)

  In strong acids, molecules disassociate (break up) completely into ions when they dissolve in water which produces a high concentration of hydrogen ions and therefore a lower pH. In weak acids, molecules don't disassociate completely into ions which produces a lower concentration and a lower pH.
• Explain how the pH and reactivity of an acid depend on the concentration and the strength of the acid.

  The higher the concentration of hydrogen ions, the lower the pH so the more reactive it is while the lower the concentration of hydrogen ions, the higher the pH so the less reactive it is.
• How does a base react in a neutralisation reaction?

  It accepts H+ ions so the pH becomes neutral.
• What happens when an acid reacts with a metal oxide?

  Salt and water are produced.
• What is the word equation for the reactions of acids with metal oxides?

  Acid + Metal Oxide → Salt + Water.
• Write a symbolic equation of an example of a metal oxide reacting with an acid.

  Magnesium oxide + acid → magnesium sulfate + water.

  MgO (s) + H2SO4 (aq) → MgSO4 (aq) + H2) (l).
• What happens in a neutralisation reaction?

  Acid reacts with base to form salt and water as hydrogen ions combine with oxide ions which removes the hydrogen ions so the pH increases and becomes neutral.
• What are the steps involved in preparing a soluble salt from an acid and an insoluble reactant?(titration)

  Tin oxide can be prepared by reacting with hydrochloric acid.

  
  

  1)add excess tin oxide to hydrochloric acid.

  2)gently warm the mixture to speed up the reaction.

  3)filter to remove the unreacted solid from the solution.

  4)heat to evaporate water and concentrate the salt solution.

  5)leave water to evaporate and crystallisation to take place.
• Why is an excess of insoluble reactant used when preparing a soluble salt?

  To ensure all the soluble reactant is used up.
• Why is the excess reactant removed when preparing a soluble salt?

  It is to make the salt pure.
• Why does the remaining solution only contain a salt and water?

  The mixture is filtered to remove the residue from filtrate which leaves salt and water.
• What are the chemical formulas of some common compounds?

  Water: H2O

  Carbon dioxide: CO2

  Sodium chloride: NaCl

  Methane: CH4
• What are state symbols and how are they used?

  State symbols in chemistry indicate the physical state of a substance in a chemical equation. They are used to show whether a substance is in a solid (s), liquid (l), gas (g), or aqueous solution (aq) state.
• How do you balance equations?

  To balance equations, you can add large numbers infront of elements and are not allowed to add small numbers.

  Example: Balance

  Calcium oxide + hydrochloric acid ---> calcium chloride + water

  CaO + _HCl ---> CaCl2 + H2O

  Answer: CaO + 2HCl --> CaCl2 +H2O

  2 atoms of hydrogen in H2O and 2 atoms of chlorine in calcium chloride so to balance add a 2 before HCl so there are 2 atoms of hydrogen and 2 atoms of chlorine on the left side too.
• Give examples of alkalis that are soluble bases?


  Sodium hydroxide, potassium hydroxide, calcium hydroxide.
• Describe the reaction of acids with alkalis?

  Neutralization.
• What happens to the ions in an acid and alkali during neutralization?

  The hydrogen ions in an acid (H+) react with hydroxide ions in an alkali (OH-) to form water (H2O).

  H+ (aq) + OH- (aq) ---> H2O (l).
• Why is titration used to prepare soluble salts?

  Separation of excess reactant becomes impossible so titration makes all reactants the exact amount.
• How to carry out an acid-alkali titration?

  1)Measure set amount of acid in a conical flask using a pipette and add a few drops of indicator.

  2)Slowly add alkali to acid using burette until end point when acid is completely neutralised.

  3)Repeat first two steps but with alkali but no indicator. so salt won't be contaminated with indicator.

  4)solution remaining contains only salt and water and evaporate crystals, then filter off solid salt.
• How do you write a balanced ionic equation?


  Separate the reactants and products into their respective ions and balance the charges.

  Example: Balance

  Ca2+ + Cl2- +F2 ---> Ca2+ +2F- + Cl2

  Delete the formula of any spectator ions (meaning ions that have not changed at all during the reaction) which in this equation is Ca2+.

  Answer: Cl2- + F2 ---> 2F- + CL2