CC8: Acids and alkalis

• Are alkalis soluble bases?

  Yes

  they dissolve in water to produce hydroxide ions (OH-)
• what is the effect of alkalis and acids on indicators?

  alkaline:

  litmus: blue

  methyl orange: yellow

  phenolphthalein: pink

  acids:

  litmus: red

  methyl orange: red

  phenolphthalein: colourless
• how can you change a concentrated solution to a dilute solution?

  add water or solvent
• how can you change a dilute solution to a concentrated solution?

  dissolve more solute into it or evaporate some of the water from it
• How do you carry out an acid-alkali titration?

  STEP 1: put acid into the pipette

  STEP 2: put a known volume of alkali into a conical flask using the pipette

  STEP 3: put a few drops of indicator into the alkali (phenolphthalein or methyl orange)

  STEP 4: record the brunette start reading

  STEP 5: add the acid to the alkali until there is a colour change (the end point)

  STEP 6: record the burette end reading
• how do you prepare a dry, pure sample of an insoluble salt?

  STEP 1: put the two solutions into a beaker

  STEP 2: filter the mixture

  STEP 3: rinse the beaker with a bit of distilled water and pour it through the funnel

  STEP 4: pour more distilled water over the precipitate into the funnel

  STEP 5: remove the filter paper with the precipitate and dry it in a warm oven
• how do you prepare a soluble salt from an acid and an insoluble reactant?

  STEP 1: react the warm acid and a metal oxide powder

  STEP 2: filter the mixture and removed unreactive metal oxide

  STEP 3: hit the mixture in an evaporating basin over because of boiling water over a Bunsen burner and heat until evaporated, which produces the salt
• how does PH depend on the concentration and strength of an acid?

  Concentration = pH increases = higher acidity
• does reactivity depend on the concentration and strength of an acid?

  Concentration increases = reactivity increases
• how does the base react in a neutralisation reaction?

  The base neutralises the acid by giving it hydroxide ions to the acid to neutralise the hydrogen ions in the acid
• what is pH affected by concentration in acids?

  Increase number of hydrogen (H+) ions = higher concentration = more acidic = lower pH
• how is pH affected by concentration in alkalis?

  Increase number of hydroxide (OH-) ions = increased concentration = more alkaline = higher pH
• how is pH affected by concentration in neutral solutions?

  Neutral solutions of a pH of seven and has equal concentrations of H+ and OH- ions
• recall the chemical formula for some common compounds

  sodium chloride (table salt) = NaCl

  Methane = CH4

  Oxygen gas = 02

  Hydrochloric acid = HCl

  Sulphuric acid = H2SO4

  Nitric acid = HNO3
• what are the general rules solubility of common substances in water?

  Soluble in water:

  • All common sodium potassium in ammonium salts
  • All nitrates
  • Most chlorides
  • Most sulfates
  • Sodium potassium and ammonium carbonate
  • Sodium potassium is ammonium hydroxides

  Insoluble in water:

  • Silver, lead chlorides
  • Lead, Barium, calcium sulfates
  • Most carbonates
  • Most hydroxides
• what are the pH values associated with acidic, alkaline and neutral solutions?

  0 to 6 = acidic

  7 = neutral

  8 to 14 = alkaline
• what do the state symbols mean?

  S = solid

  L = liquid

  G = gas

  Aq = aqueous ( dissolved in water)
• what happens during a neutralisation reaction?

  Hydrogen ions in an acid reacts with the oxide ions to form water

  The acid loses its hydrogen ions and becomes more neutral as the pH increases

  Salts are produced by replacing the hydrogen ions with metal ions
• what happens when an acid reacts with a metal oxide?

  Metal oxide + acid ——> salt + water

  MASH
• What is a precipitate?

  An insoluble substance that is formed when two soluble substances react together in a solution
• What is a strong acid?

  an acid that fully dissociates into ions in a solution and all release H+ ions

  e.g: hydrochloric acid and sulfuric acid
• what is a weak acid?

  And I said that has only partially dissociated into ions and only a few molecules release H+ ions

  e.g: ethanoic acid
• What is the test for carbon dioxide?

  lime water test:

  STEP 1: placed the substance into one test tube and lime water into another

  STEP 2: wait until the gas as bubbled through the delivery tube and into the lime water

  STEP 3: if it goes cloudy/milky, the white precipitate has formed and carbon dioxide is present
• what is the difference between a dilute and concentrated solution?

  Concentrated solution have a greater amount of dissolved solute particles than a dilute solution
• what is the difference between strong and weak acids?

  Strong acids have a higher concentration of H+ ions than weak acids and therefore had a lower pH then the weak acids at the same concentration
• what is the general equation between an acid and a metal to produce a salt and hydrogen?

  Acid + metal ——> salt + hydrogen gas

  Metal ions in the metal replace the hydrogen ions in the acid to make the salt, the displacement of the hydrogen ions from the acid creates the hydrogen gas
• what is the general reaction between a metal carbonate and an acid to produce salt, water and carbon dioxide?

  Acid + metal carbonate ——> salt + water + carbon dioxide

  Hydrogen ions from the acid reacts with the carbonate ions in the metal carbonate to make water is reaction that produces carbon dioxide, gas and a salt
• what is the relationship between hydrogen ion concentration and pH?

  Higher concentration of H + = lower pH
• what is the test for hydrogen?

  Squeaky pop test:

  STEP 1: put the gas into a test tube, all the reactants that make the gas

  STEP 2: place a lit splint into the test tube

  STEP: if the gas is hydrogen, that will be a squeaky pop
• which ions are present in all acidic solutions?

  Hydrogen ions (H+)
• Which ions are present in all alkaline solutions?

  Hydroxide ions (OH-)
• why do you add an excess of insoluble reactant when preparing a soluble salt?

  To ensure all the acid is used up
• is there an excess reactant removed one preparing a soluble salt?

  To ensure the salt is pure, as there is only salt and water left
• why is titration used to prepare soluble salts?

  • Precise control over amounts of reactants
  • Controlled reaction (you can slowly add one solution to another0