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Presentation On Reactions Of Acids

Published in: Chemistry | Science
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This PPT is suitable for the IGCSE and O Level Chemistry students. It only provides theoretical background of the topic. The worksheets and topical questions will be discussed during the tutoring sessions

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  1. Reactions of Acids Chemistry (IGCSE / O-Level)
  2. What will you learn in this lesson? • Describe the characteristic properties of acids in terms of their reactions with: (a) metals (b) bases (c) Carbonates • Strong and weak acids • Acid as proton donor and base as proton acceptor
  3. Reactions of Acids There are three major chemical reactions in which all acids will take part. These reactions are best seen using dilute acid solutions. In these reactions, the acid reacts with: • A reactive metal (e.g. magnesium or zinc) • A base (or alkali) • A metal carbonate or hydrogen carbonate b: Zinc reacting hydrochloric acid and
  4. Reaction of Acids with Metals Reactive metals can be used to displace hydrogen from the acid metal + acid -s salt* hydrogen Reaction is violent with the use of very reactive metal such as sodium or calcium No reaction occurred with less reactive metals such as copper Reaction is very slow with moderately reactive metals such as lead
  5. Reaction of Acids with Metals (contd.) The salt made depends on the acid reacted with the metal: • hydrochloric acid always gives a chloride • nitric acid always gives a nitrate sulfuric acid always gives a sulfate. magnesium + nitric acid Mg(s) + 2HNOa(aq) zinc -F hydrochloric zu(s) + 2HC1(aq) magnesium + zinc chloride + ZnCb(aq) + hydrogen H2(g) hydrogen H2(g)
  6. Reaction of Acids with Bases and Alkalis This is neutralization reaction + H 200) acid + base —s salt + water hydrochloric + sodium sodium chloride + water HC1(aq) + NaOH(aq) - NaC1(aq) + HQO(I) If mixed in correct amounts then the alkali exactly neutralizes the acid Neutralization may also occur when insoluble base reacts with acid magnesium + nitric acid — magnesium 4- water Mg0(s) + 2HNOa(aq) — + H20(1)
  7. Reaction of Acids with Bases and Alkalis (contd.) sodium hydroxide (NaOH) potassium hydroxide (KOH) magnesium oxide (MOO) pper oxide (Cuc) So d urn Hydrochloric acid (HCI) sodium chloride, Naa potassium chloride, KCI magnesium chloride, MgC;la copper chloride, CuC12 Nitric acid (HN03) sodium nitrate, NaN03 potassium nitrate, KNOB magnesium nitrate, copper nitrate, the •mes from (he bas-eon alkali in this case Sulfuric acid (H2S04) sodium sulfate, NazS04 potassium sulfate, K2S04 magnesium sulfate, t49S04 copper sulfate, CuS04 the non-metatlic part comes from fhe acid in Case
  8. Reaction of Acids with Carbonates All carbonates give off carbon dioxide when they react with acids. E.g., effervescent antacid tablets. The result is to neutralize the acid and produce s It solution acid + metal carbonate -€ salt + water + carbon dioxide To produce carbon dioxide in lab hydroåloric acid + calcium carbonate czacium chloride water + carh»u 2HC1(aq) + CaCOJ(s) CaC12(aq) + + C02
  9. Reaction of Acids with Carbonates (contd.) The test for carbonate is also based on this type of reaction. Dilute hydrochloric acid is added to the unknown salt and if the carbon dioxide is given off then the salt is carbonate Anc carbonate -F hydrochloric acid zinc cmoride -f- water + carbon dioxide + 2HC1(aq) ZuC12(aq) C02(g)
  10. Strong and Weak Acids acids have higher • Stronger concentration of H + ions, higher acidity, and lower pH value • Weaker acids have lower concentration of ions, lower acidity, and higher pH value • The difference lies in the ionic nature of acid solutions i.e. the concentration of ions in solution • Each pH unit means a ten-fold difference in ions concentration Strong Weak Acids
  11. Strong and Weak Acids (contd.) The separation of a covalent molecule into ions when dissolved in water is called dissociation Some acids dissociate completely into ions HC1(g) H+(aq) + Cl-(aq) W(aq) + -(aq) HNOa(1) H+(aq) + Noa -(aq) In some acids (methanoic acid, ethanoic acid, carbonic acid and citric acid etc) only a small fraction of covalently bonded molecules are dissociated into ions COOHi1) most molecules H+(aq) + CHs COO-(aq) only a small number of are dissociated into ions at any one time
  12. Strong and Weak Acids (by Definition) Strong Acid: An acid that is completely ionized when dissolved in water — this produces the highest possible concentration of (aq) ions in solution. They are strong electrolytes such as HCI, HN03 Weak Acid: An acid that is partially dissociated when dissolved in water — this produces a lower concentration of (aq) ions in solution. They are weak electrolytes such as acetic acid.
  13. Properties and Comparison • The process of dissociation is reversible in weak acids • When comparing any two acid solutions, their concentration should be same. If the concentrations are same, we can use pH, the conductivity or the rate of a particular reaction to hel decide the extent of ionization 1 IS: of a (hydmd'hric add) Mt a the right.
  14. Ions in Neutralization acid + alkali —s salt + water sodium HCJ(aq) + NOOH(aq) — NaCl(aq) W (aq) + OH (aq) hydroge n ions hydroxide ions ions in hydrochloric H20(1) w ater 'spectator ions' water
  15. Ions in Neutralization (contd.) In neutralization reactions acid provide H + ions to react with hydroxide ions. While, base is supplying OH - ion to accept the ions and form water. a hydrogen atom a hydrogen ion (H*) (the electron has been lost, leaving just the proton of the nucleus) A hydrogen ion is Simply a proton,
  16. Ions in Neutralization (contd.) 'This to a further definition of an acid and a base in terms of hydrogen ion (proton) trensfen • proton, to A base) • ion, from an •cid).
  17. Practice Questions XO Define an acid and using the ideas Of proton (H + ion) transfer. a Write the Ibälanzedsymbdl equationsforthe reaction betweent i copper g*de and nitric acid ii zinc *Cid b in ii Zn(S) H2(g) explÄin be regarded as redox reaction, st;te Which •reactant has been oxidised. a W6teaneqvati6ntoshowwhöthappens when hydrogen Chloride dissolvestn water. b solution has of thesame