Worksheet 20 answers

Worksheet 20 answers - ‘ Worksheet 20 — Acids and Bases...

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Unformatted text preview: ‘ Worksheet 20 — Acids and Bases The Bronsted-Lowry definition of an acid is a substance capable of donating a proton (Hi), and a base is a substance capable of accepting a proton. For example, the weak acid, HF, can be dissolved in water, giving the reaction: HF (aq) + H20 (I) 1': H30+ (aq) + F‘ (aq) acid conjugate base base conjugate acid In this reaction, HF is the species losing the proton (H+), making it the acid. Water is the species accepting the proton, to form the hydronium ion, H302 making it the base. The F'(aq) is called the conjugate base of HF. it can gain a proton in the reverse reaction. H30+ is the conjugate acid of H20, since it can lose a proton in the reverse reaction. The stronger an acid, the weaker its conjugate base will be and the stronger the base, the weaker its conjugate acid. The equilibrium concentrations of these species will be determined by the relative strengths of the acids and bases. The strongest acid will dissociate to the greatest extent. H30” (H) is the strongest acid that can exist in an aqueous system. So, the equilibrium in this system will favor the reactants, HF and H20, the weaker acid and base. The equilibrium state is described by an equilibrium constant, K3, in the case of acids, and Kb in the case of bases. These are related by the expression KW = Ka x Kb = 1 x 10'”. 1. Classify the following as Brensted acids, bases or both. d) NHffiaa" 8) NH; M f) 0032* W ‘ Wft-b ”H3 lul‘LarbaA/Hi (03" "4 H601” H my =7 A/l-i 5"" 2. What is the conjugate base of the following acids? a) HCIO4 b) NH4+ 0) H20 d) HCOg‘ owe" Alt/3 o/f’ . 6'03, 3 3. What is the conjugate acid of the following bases? a) CN‘ b) s042' 0) H20 d) H003; [TC/Ur H504! #30 % [712(05 4. H805 is amphoteric; it can behave as either an acid or a base. In the examples above, you may have noticed that H20 and HCO3' can also exist as acids or bases. a) d) Write the equation for the reaction of H801; with H20 in which it acts like an acid and identify the acid base pairs. Circie the strongest acid. Then write an expression for Ka The value of Ka at 25° C Is 1. 23 x 10. 7 Use an arrow to indicate side Is favored by the equilibrium ,4 5293' +2910 :3 we (a 5 [&0¢][§0f‘] 5a [grog-7 4/ "z /,25x /o’7 Write the equation for the reaction of H803‘ with water in which it acts like a base and identify the acid—base pairs. Circle the strongest acid. Then write an expression for Kb. What is the value of Kb at 25° C, given that the K8 for H2803 = 1.58 x 102? Use an arrow to indicate which side is f. a - 5 .0y the equilibrium. #503." ah” l6" (my/fife}! J wk :71: a [VHSiiJg‘j .. fx/OJ’. .- 6r§i¥/‘I #511 10" if H803 is placed in water is the resulting soiution acidic or basic? K; < {a 4&1an gma Compute a value for the equilibrium constant for the reaction shown below: My K { 3032'® Hsoaszo K= $5” ’0 79w LOW/W 35%.“) ’8' //ga’ //("12%x/0 fjé’X/O Circle the strongest acid and indicate which side is favored by the equilibrium. When Li20 is dissolved in water, the solution turns basic from the reaction of oxide, 02', with water. Write the reaction and identify the acid— base pairs in the reaction 1430+?!“ 0 “‘ngéffo Mao—9414” 029 *0/7’“ LLJC::J;’:,J 5—4 5b 6. Identify the conjugate acidabase pairs in the following reactions. Circle the strongest acid and indicate which side is favored at equilibrium: 3) NH4+ + H20 3 NH3 + H30+ . MA - i m 5!? :56: as!” b) HC OH+C '3 HCOO'+ HCN KaHCOOH =_1.8x10'5é/flmfl day 645 we Ka HON: 6.2x 10-15 SM 5; w 6) NH; + 0032' : NH3 + H003' Kb NH3 : 1.8 x 10'5 s}: W; M18x10‘4 5/7”?” W 551 m: fl d HPO"+OH‘SHP02'+HO " 1' ) 2 43b [:17 2 #2,”; Sam/M am/ so it 3, 50k Mam flpflf We, 7'. Name 6 strong acids. Name 6 strong bases. . W Ma 5H 65 OH , (a 0 W /C 6 H T“ [f m f $75} ' Hf ”12/53.? 44' W4 9/ air); 44-10 .MC, Wm; {19 UH fl" (‘9 9/ [WK/4 Complete the following table, which deals with pH, {H+], acidity, neutrality and basicity. pH [H1 solution is: <7 > Alf/Oi? flaétc' 9 < 1.0 X107 dine . , - xi §L ’ /X/0 neutral 10. Catcutate the pH of the solution formed when 100 mL of 1.00 M HCI is addedtoTDOLofwater. /06’X focgé X ”02) 21/747: , /O*0 ”1-7? #7 Z, ., 4 + ”MM/7’ : {0909/4 W Ml—zw //J{‘)7L/ /C90: Calculate the pH of the fotlowing solutions of strong acids and bases: a) 0.001 M HCI b) 0.75 M KOH (#0 = /x M'fu [5W] ,. , 9/ M p/'/73& farm/fl C) 2.8x 104M Ba(OH)2 ffi " A720”? [0/7“] ,- 2&2, Xx MM”):— ELK/W0”? Kai/7’ ; .5” a? S’— / #2 /0’, 5t!“ ...
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