YEAR 12 HOMEWORK
SHEET 5 - Acids and Bases
Read pp 29 - 38 of Chemistry 2
A good resource is the online chemistry course at:
http://tqd.advanced.org/3310/lographics/index.html - esp Unit 2 Section 2 (Acid/Base Reactions) and Unit 7 Section 5 (Acid-Base Basics).For these questions you must need to remember n=m/M, n=cV and pV=nRT and the table of solubilities.
Q1. Name the acids and give the conjugate base of the following:
(a) HCl (b) H
2SO4 (c) HNO3 (d) H2O (e)CH3COOH (f) H2SO3
Q2. Name the bases and give the conjugate acid of the following:
(a) KOH (b) NH3 (c) Cl
- (d) NaHCO3 (e) Na2CO3 (f) NaOH
Q3. For each of the following reactions - state whether the first named reactant is acting as an acid or a base or neither.
(a) H2SO
4 (aq) + 2KOH (aq) ---> K2SO4 (aq) + 2H2O (l)(b) CuCl2 (aq) + 2NaOH (aq)
---> Cu(OH)2 (s) + 2NaCl (aq)(c) 3NH3 (aq) + H3PO4 (aq)
---> (NH4)3PO4 (aq)(d) 2HCl (aq) + Mg (s)
---> MgCl2 (aq) + H2 (g)(e) Ca(OH)2(aq) + CO2 (g)
---> CaCO3 (s) + H2O (l)
Q4. Calculate the concentration of the following.
(a) 18.0 g of potassium bromide is dissolved in water to form 250ml of solution.
(b) 10.0 ml of 0.53 M NaOH is diluted to a final volume of 250 ml
(c) 10.0 L of HCl gas at 20oC and 1.1 atm is dissolved in 200 ml of water
Q5. What mass of solute is needed to prepare
(a) 2.0 L of 0.100M sodium hydroxide solution
(b) 100 ml of 0.125 M potassium permanganate solution?
(c) 20 ml of 0.0250M Na2CO3.10H2O
Q6. A student standardised a solution of ethanoic acid by using 0. 0957M sodium hydroxide solution with methyl orange to detect the endpoint. 20.00 ml of the hydroxide reacted with and average of 12.3 ml of the acid.
(a) Draw a flowchart of the steps involved in the titration
(b) Write the chemical reaction
(c) Calculate the concentration of the acid
(d) Why is the methyl orange added?
(e) Is the sodium hydroxide a primary standard? Explain.
Q7. An aliquot of 25.0 ml of 0.0500 M nitric acid is neutralised by 17.1 ml of sodium carbonate solution.
(a) Write the chemical reaction.
(b) What is the concentration of the base solution?
(c) What effect (if any) would the following "errors" have on the final result
(i) The pipette is rinsed with distilled water
(ii) The pipette is rinsed with the acid solution
(iii) The conical flask is rinsed with the sodium carbonate solution
(iv) The conical flask is rinsed with water
(v) The student left an air bubble in the burette
Q8. Potassium hydrogen phthalate KH(C8H4O4) is a monoprotic primary standard (ie it donates one proton to a base). It was found that 2.024g of potassium hydrogen phthalate requires 22.06 ml of potassium hydroxide solution to neutralise it.
(a) Write an equation for the neutralisation.
(b) What is the concentration of the KOH solution?
Q9. A 20.0 ml sample of vinegar (containing ethanoic acid) was diluted to 250.0 ml in a standard flask. A 20.0 ml aliquot of this solution required 19.75 ml of 0.0452M NaOH to reach the endpoint. calculate the mass of acetic acid in the vinegar and from this calculate the % composition (m/v).
Q10. To analyse the ammonia content of a brand of floor cleaner, 10.00 g of the cleaner was weighed and diluted to 250 ml in a standard flask. 20.0 ml aliquots of the diluted cleaner were reacted with 20.0 ml aliquots of 0.0987M HCl. The excess HCl required 3.88 ml of 0.0489M NaOH to be neutralised.
(a) What type of titration is this? Why is it used?
(b) Calculate the No moles of HCl in the 20 ml aliquot.
(c) Calculate the No moles of HCl in excess
(d) Calculate the number of moles of HCl consumed by the reaction with NH3
(e) Calculate the no moles of NH3 reacted in the 20.0 ml aliquot.
(f) What mass of ammonia was in the standard flask
(g) What was the % of ammonia in the cleaner (by mass)
Q11.What is the difference between
(a) Strong and weak acids
(b) End point and equivalence points
(c) Volumetric and gravimetric analysis
(d) Primary and Secondary standard