3 Acids and bases - 3 ACIDS AND BASES 3.1 pH and Kw 3.2 pH and acids 3.3 pH and bases 3.4 Acid-base titrations 3.5 Buffer solutions 3.6 More complex

3 Acids and bases - 3 ACIDS AND BASES 3.1 pH and Kw 3.2 pH...

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3. ACIDS AND BASES3.1. pH and Kw3.2. pH and acids 3.3. pH and bases 3.4. Acid-base titrations 3.5. Buffer solutions 3.6. More complex buffer calculations Acids and bases answers
3.1. pH and K1.Complete the table below showing some numbers and their common logarithmic values; (1 mark) Number (n) log100.001 ……….. 0.1 ………..………..0 ………..3 2.Calculate the pH (to 2 dp) of each of the solutions below: (3 marks) (2 marks)(a) (b) (c) pH = ..........pH = ..........pH = ...........w
n3.As water is always slightly ionised, we can write the following equilibrium for water; H2O(l) H+(aq) + OH(aq) ΔH = +iveAs only a very small amount of the water is ionised, we define a new equilibrium constant for this equilibrium called the ionic product of water, KwKw= [H+(aq)] [OH(aq)] Like any other equilibrium constant, the value of Kwdepends on the temperature of the equilibrium. (a) Predict what effect increasing the temperature will have on the pHof pure water. ; ...........................................................................................................................................(1 mark) (b) Calculate the pH of pure water (to 2 dp) at each of the temperatures below; (i) 10 C, Kw= 0.29 × 10–14mol2dm–6............................................................................................(ii) 25
(iii) 40 C, Kw= 2.92 × 10–14mol2dm–6.............................................................................(3 marks) (c) Complete the paragraph below; As the temperature decreases, water becomes (more acidic / less acidic / remains neutral). Explain your answer
.........................................................................................................................................(2 marks)(a) (b) (c) pH = ..........pH = ..........pH = ...........
3.2. pH and acids1.Identify the species formed when the following act as acids; (a) HCl ...........................(b) NHŸ...........................(c) HCO........................
(3 marks) 2.Calculate the pH (to 2 dp) of the following acids; (a) 0.25 mol dm–3HCl ...............................................................................................................(1 mark) (b) 0.004 mol dm–3NaHSO4, Kaof HSO= 1.00 × 10–2mol dm–3 .........................................................................................................................................................................................................................................................................................................................................................................................................................................................(2 marks) 3.Calculate the concentration of the following acids given their pH. (a) HCl, pH 0.65 .......................................................................................................................(1 mark) (b) H2SO4,pH 2.61 ...................................................................................................................(1 mark) (c) CH3COOH, pH 3.40, Ka1.7 × 10–5mol dm–3 .........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2 marks)
3.3. pH and basesDefine; (a) a Brønsted-Lowry acid ...............................................................................................................................................................................................................................................................(1 mark) (b) a Brønsted-Lowry base ...............................................................................................................................................................................................................................................................Acids and bases 3.3. H++CCNHHHHHHHCCN+HHHHHHHH1.Define; (a) a Brønsted-Lowry acid ...............................................................................................................................................................................................................................................................(1 mark) (b) a Brønsted-Lowry base ...............................................................................................................................................................................................................................................................(1 mark) 2.In the following acid-base reactions identify the reactant species(ion or molecule) acting as a Brønsted-Lowry base;
O
CO2(3 marks) 3.Calculate the pH (to 2 dp) of the following basic solutions (take Kwto be 1.00 × 10–14mol2dm–6); (a) 0.150 mol dm–3NaOH .................................................................................................................................................................................................................................................................(1 mark) (b) 0.261 mol dm–3Mg(OH)2.............................................................................................................................................................................................................................................................(1 mark) 4.Calculate the concentration of the following basic solutions (take Kwto be 1.00 × 10–14mol2dm–6); (a) KOH, pH 11.00............................................................................................................................................................................................................................................................................(1 mark)

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