Chapter 8 part 1 : Acids Flashcards
What is an acid?
- An acid is a substance that produces hydrogen ions (H+) when dissolved in water.
What are the names and chemical formulae of some common acids?
- Hydrochloric acid:
Chemical formula: HCl - Nitric acid:
Chemical formula: HNO3 - Sulfuric acid:
Chemical formula: H2SO4 - Ethanoic acid:
Chemical formula: CH3COOH
Do all acids produce hydrogen ions (H+) in an aqueous solution?
- Yes, all acids produce hydrogen ions (H+) in an aqueous solution.
- E.g. HCl (aq) –> H+ (aq) + Cl (aq)
- E.g. HNO3 (aq) –> H+ (aq) + NO3- (aq)
- E.g. H2SO4 (aq) –> 2H+ (aq) + SO4 (square 2-) (aq)
- E.g. CH3COOH (aq) –>/<– H+ (aq) + CH3COO- (aq)
What are some properties of acids?
Acids:
- Have a sour taste.
- Conduct electricity due to the mobile ions produced when they dissolve in water.
- Turn blue litmus paper red.
- E.g. Lemons, oranges, hydrochloric acid, nitric acid, sulfuric acid, etc…
How are salts formed?
- Acids react with some metals to form salts and hydrogen gas, and salts are also ionic compounds.
** Acid + metal –> salt + hydrogen ** - E.g. Hydrochloric acid + magnesium –> magnesium chloride + hydrogen
= 2 HCl (aq) + Mg (s) –> MgCl2 (aq) + H2 (g) - E.g. Sulfuric acid + sodium –> sodium chloride + hydrogen
= H2SO4 (aq) + 2Na (s) –> Na2SO4 (aq) + H2 (g)
How can acids react to form salts and hydrogen gas?
- Acids react with some metals to form salts and hydrogen gas.
- Salts are ionic compounds.
** Acid + metal –> salt + hydrogen ** - E.g. Hydrochloric acid + magnesium –> magnesium chloride + hydrogen
2 Hcl (aq) + Mg (s) –> MgCl2 (aq) + H2 (g) - E.g. Sulfuric acid + sodium –> sodium sulfate + hydrogen
H2SO4 (aq) + 2Na (s) –> MgCl2 (aq) + H2 (g) - E.g. Sulfuric acid + sodium –> sodium sulfate + hydrogen
H2SO4 (aq) + 2Na (s) –> Na2SO4 (aq) + H2 (g)
How can the hydrogen gas produced during an acid and metal reaction be identified?
- The hydrogen gas produced during the reaction of an acid with a metal can be identified by testing it with a burning splint.
- The burning splint will then extinguish with a ‘pop’ sound.
What is an Acid + base –> salts + water reaction?
- Acids react with bases to from salts and water.
- E.g. of bases: Metal oxides and metal hydroxides.
**Acid + base –> salt +water ** - E.g. Nitric acid +magnesium oxide –> magnesium nitrate + water
2HNO3 (aq) + MgO (s) –> Mg (NO3)2 (aq) + H2O (l) - E.g, Hydrochloric acid + potassium hydroxide –> potassium chloride + water
HCL (aq) + KOH (aq) + H2O (l)
What is a neutralisation reaction?
- A neutralisation reaction is the reaction between an acid and a base.
What is an Acid + carbonates
–> salts + water + carbon dioxide reaction?
- Acids react with carbonates to form salts, water and carbon dioxide gas.
** Acid + carbonate –> salt + water + carbon dioxide ** - E.g. Hydrochloric acid + sodium carbonate –> sodium chloride + water + carbon dioxide
2HCl (aq) + NaCO3 (s) –> 2NaCl (aq) + H2O (l) + CO2 (g)
-E.g. Nitric acid + calcium carbonate –> calcium nitrate + water + carbon dioxide
2HNO3 (aq) + CaCO3 (s) –> Ca (NO3)2 (aq) + H2O (l) + CO2 (g)
How can the carbon dioxide gas be identified during an acid and carbonate reaction?
- The carbon dioxide gas produced during the reaction of an acid with a carbonate can be identified by bubbling it through limewater.
What is the salt formed in the reactions of/with acids?
The salt formed in the reactions of acids is:
- A chloride if hydrochloric acid is the reactant.
- A nitrate if nitric acid is present.
- A sulfate if sulfuric acid is the reactant.
What are some basic examples of strong and weak acids?
- Strong acids are hydrochloride acid (HCl), nitric acid (NHO3), and sulfuric acid (H2SO4).
- Weak acids are ethanoic acid (CH3COOH).
How do strong and weak acids ionise in an aqueous solution?
- Strong acids ionise completely in aqueous solutions.
- E.g. When 1 ole of HCl is dissolved in water, HCl ionises completely to form 1 mole of H+ ions, and 1 mole of Cl- ions.
HCl (aq) –> H+ (aq) + Cl- (aq) - Weak acids ionise partially in aqueous solutions.
- E.g. When 1 mole of CH3COOH is dissolved in water, only a small amount of CH3COOH ionises partially to form H+ ions, and CH3COO- ions. Thus, at anytime there will be a mixture of CH3COOH molecules, H+ ions, and CH3COO- ions.
**CH3COOH (aq) –>/<– CH3COO- (aq) + H+ (aq) **
What does the “strength of an acid” mean?
- The strength of an acid means the extent of the ionisation of the acid in the aqueous solution, the smaller the extent of ionisation, the weaker the acid.
** - smaller = weaker - larger = stronger
