4- Acids and Redox Flashcards
What are the common acids?
Hydrochloric acid - HCl
Sulfuric acid - H2SO4
Nitric Acid - HNO3
Ethanoic Acid - CH3COOH
What are acids? What happens when they are dissolved in water?
-Proton donors
-They release hydrogen ions (H+) as protons when dissolved in water
What is the equation for acids dissolving in water? Give the example of HCl
HA + H20 ⇌ H+ + A-
HCl + H20 → H+ + Cl-
What is an example of a strong acid? How does it react with water?
-HCl, H2SO4, HNO3
-Strong acids release all there hydrogen atoms into a solution as H+ ions (forward reaction favoured sp lots of H+ formed)
-completely dissociates in aqueous solution
HCl → H+ + Cl -
What is an example of a weak acid? How does it react with water?
-Ethanoic acid (CH3COOH)
-Only releases a small proportion of its available hydrogen atoms into solution as H+ ions (backward reaction is favoured so not as may H+ protons produced)
-only partially dissociates in aqueous solution
CH3COOH (aq) ⇌ H+ (aq) + CH3COO- (aq)
What is an alkali? What is the overall equation and example of reaction with NaOH?
A base that dissolves in water releasing OH- ions into the solution
B + H20 ⇌ BH+ + OH-
NaOH + H20 ⇌ Na+ + OH-
What does a base do?
-neutralises an acid to form a salt
What happens when an alkali (base) dissolves in water?
-releases hydroxide (OH-) ions into the solution
-NaOH + H20 → Na+ + OH-
What are some examples of common bases?
-Sodium hydroxide NaOH
-Potassium hydroxide KOH
-Ammonia NH3
What is an example of a strong base? What happens when they react with water?
-NaOH , KOH
-forward reaction is favoured is favoured, lots of OH- ions formed
NaOH ⇌ Na+ + OH-
What is an example of a weak base? What happens when they react with water?
-Ammonia NH3
-backward reaction is favoured, not as may OH- ions formed, only partially dissociates
NH3 + H20 ⇌ NH4+ + OH-
What is a polyprotic acid? And examples
-An acid which donated more then one proton (H+)
-H2SO4 is diprotic (1 mol of H2SO4 donates 2 moles of H+)
-H3PO4 is triprotic (1 mol of H3PO4 donates 3 moles of H+)
What are examples of common metal oxides?
-MgO
-CaO
-CuO
What are examples of common metal carbonates?
-Na2CO3
-CaCO3
-CuCO3
What happens when an acid and base reacts in a neutralisation reaction?
acid + base → salt + water
-H+ ions react with the OH- ions produced from the base (alkali) to form a salt and neutral water
-H+ ions from the acid are replaced by the metal or ammonium ions from the base
-salt is made from the metal from the base and the non metal from the acid
H+ + OH- → H20
HCl + LiOH → LiCl + H20
HNO3 + KOH → KNO3 + H20
What happens when ammonia reacts with a base (alkali)?
-reacts with acids to make ammonium salts but no water
2NH3 + H2SO4 → (NH4)2SO4
How does ammonia react with water?
-doesn’t produce OH- ions directly
-ammonia reacts with H2O first and accepts a proton to produce an ammonium ion (NH4+) and OH- ions
NH3 + H20 ⇌ NH4+ + OH-
What is the fill equation and ionic equation of HCl (acid) reacting with NaOH (alkali) ?
full equation -
HCl + NaOH → NaCl + H20
H+ + OH- → H20
What is the general reaction of a metal reacting with an acid?
Metal + Acid → Salt + Hydrogen
What is the equation and ionic equation for Calcium (metal) reacting with H2SO4 (acid)?
Ca + H2SO4 → CaSO4 + H2
Ca + 2H+ → Ca2+ + H2
What is the general reaction of a metal oxide reacting with an acid?
Metal oxide + acid → salt + water
What is the equation and ionic equation for magnesium oxide reacting with HCl (acid)?
MgO + 2HCl → MgCl2 + H20
MgO + 2H+ → Mg 2+ + H2O
What is the general reaction of a metal hydroxide reacting with an acid?
metal hydroxide + acid → salt + water
What is the equation and ionic equation for sodium hydroxide reacting with sulfuric acid?
2NaOH (aq) + H2SO4 (aq)→ NaSO4 + 2H2O
2 OH- (aq) + 2H+ (aq) → 2H2O
What is the general equation for the reaction of an acid with a metal carbonate?
Metal carbonate + Acid → Salt + Carbon dioxide + Water
What is the equation and ionic equation for lithium carbonate reacting with nitric acid (acid)?
LiCO3 (s) + 2HNO3 (aq) → 2LiNO (aq) + CO2 (g) + H2O (g)
LiCO3 (s) + 2H+ (aq) → 2Li+ (aq) + CO2 (g) + H2O (g)
What do H+ ions and OH- ions form when reacting together?
Neutral water
What can titrations be used for?
-finding the concentration of a solution
-identification of unknown solutions
-finding the purity of a substance
What is a standard solution?
A solution of known concentration
What is the typical tolerance of a 100cm3 volumetric flask?
±0.20 cm^3
What is the typical tolerance of a 250cm3 volumetric flask?
±0.30 cm^3
What is the method for preparing a standard solution?
- Weigh out the solid precisely using a balance and a weighing boat
- Transfer the solid from the weighing boat to a beaker.
- Dissolve your solid fully using less distilled water than will be needed to fill the volumetric flask to the mark. Stir to ensure the solid is dissolved fully with a glass rod
- Transfer your solid to a volumetric flask. Use a funnel to avoid spillage. Rinse the beaker and glass rode into the flask with distilled water to make sure all of the solution is transferred
- Using distilled water fill the volumetric drop by drop until the bottom of meniscus lines up directly with the graduation line
- Slowly, invert the flask a few times to ensure the solution is thoroughly mixed
What is the uncertainty of a 10cm3 and a 20cm3 pipette and a 50cm3 burette?
10cm3 pipette - ±0.04 cm^3
20cm3 pipette - ±0.06 cm^3
50cm3 burette - ±0.10cm^3
What is each burette reading measured to?
The nearest ±0.05cm3 , so it always had 2 decimal places
How do you carry out an acid-base titration procedure?
- Add a measured volume of one solution to a conical flask using a pipette
- add the other solution to a burette, and record the initial burette, reading to the nearest 0.05 cm³
- A few drops of indicator to the solution in the conical flask.
- Run the solution in the burette into the solution in the conical flask, swirling the conical flask throughout.
- keep going until the indicator changes colour at the end point of the titration
- Record the final burette reading. the volume of solution added from the burette is called the titre, which is calculated by subtracting the initial from the final burette reading
- A quick trial titration is carried out 1st to find the approximate titre
- the titration is repeated accurately, adding the solution drop wise as the endpoint is approached, until two accurate tires are concordant (within 0.10 cm³)
how do you work out the mean titre?
-Only use values which are concordant (within 0.10 cm³), you can reject inaccurate titres
-If you were to include all the titres in the mean, you would have lost the accuracy of the titration technique
