Calculatig the [H3O + ] or [OH ] i Aqueous Solutio (Studet textbook page 500) 11. The cocetratio of hydroxide ios, OH (aq), i a solutio at 5C is 0.150 /. Determie the cocetratio of hydroium ios, H 3 O + (aq), i the solutio. You eed to determie the hydroium io cocetratio i a aqueous solutio. You kow that [OH ] is 0.150 /. costat to solve for [H 3 O + ]. K w = [H 3 O + ][OH ] = 1.0 10 14 H3O Kw 1.010 0.150 14 14 6.67 10 / Multiplyig the calculated [H 3 O + ] by the give [OH ] gives the water costat, 1.0 10 14. Uit 4 Part B MHR 135
1. A solutio of lithium hydroxide, ioh(aq), is made by placig.00 of the base ito 1.50 of solutio. What is the cocetratio of hydroium ios, H 3 O + (aq), i this solutio at 5C? You eed to fid the cocetratio of hydroium ios, [H 3 O + ], i the solutio. You kow there is.00 of ioh i 1.50 of solutio. Calculate the ar cocetratio of ioh. Sice ioh is a strog base, [OH ] = [ioh]. costat to solve for [H 3 O + ]. ioh OH H3O V.00 1.50 1. 33 / Kw 1.010 1.33 14 15 7.5 10 / Multiplyig the calculated [H 3 O + ] ad [OH ] values gives the water costat 1.0 10 14. 136 MHR Chemistry 1 Solutios Maual 978-0-07-10604-4
13. Two solutios at the same temperature are to be compared for their hydroium io cocetratios. Solutio A has a hydroxide io cocetratio of 0.335 /, ad solutio B has a hydroxide io cocetratio of 0.85 /. I which solutio will the hydroium io cocetratio be larger? Explai your aswer. You eed to compare the hydroium io cocetratios i two solutios. You kow the hydroxide cocetratio [OH ] for the two solutios. From the expressio for the water costat, [H 3 O + ] ad [OH ] are iversely proportioal. The solutio with the smaller [OH ] will have the higher [H 3 O + ]. Compare the [OH ] for the two solutios: Solutio A: [OH ] = 0.335 / Solutio B: [OH ] = 0.85 / Sice solutio B has the lower [OH ], it must also have the higher [H 3 O + ]. Usig the expressio for the water costat, [H 3 O + ] for solutio A is.99 10 14 /. For solutio B, [H 3 O + ] is 3.51 10 14 /. Solutio B has a higher [H 3 O + ]. Uit 4 Part B MHR 137
14. Explai why the two solutios i questio 13 eed oly to be at the same temperature for the compariso to be made, ad do ot ecessarily have to be at 5C. Aswer [H 3 O + ] ad [OH ] will still be iversely proportioal eve though the K w will be differet at other temperatures. 15. I a solutio at 5C, 4.75 g of sodium hydroxide, NaOH(s), is added to eough water to create a volume of.40. What is the hydroium io, H 3 O + (aq), cocetratio i this solutio? You eed to fid the cocetratio of hydroium ios, [H 3 O + ], i the solutio. You kow there is 4.75 g of NaOH i.40 of solutio. The expressio for the water costat is K w = [H 3 O + ][OH ] = 1.0 10 14. Calculate the amout i es,, of NaOH. Use the formulac to calculate the V ar cocetratio, c, of NaOH. Sice NaOH is a strog base, [OH ] = [NaOH]. costat to solve for [H 3 O + ]. c NaOH NaOH H3O m M 4.75 g 40.00 g / 0.11875 V 0.118 75.40 0.04948 / 0.04948 / Kw 14 1.010 0.04948 13.0 10 / Multiplyig the calculated [H 3 O + ] ad [OH ] values gives the water costat, 1.0 10 14. 138 MHR Chemistry 1 Solutios Maual 978-0-07-10604-4
16. A drai cleaer is a mixture of soluble hydroxides i solutio. Would the drai cleaer be acidic, basic, or eutral? Explai your aswer usig oe or two well-reasoed seteces. Aswer Sice the hydroxides are soluble, the solutio would have a high cocetratio of hydroxide ios i solutio. As a result, the hydroium io cocetratio would be very low, which meas that the solutio is basic. 17. Verify that the hydroium io, H 3 O + (aq), cocetratio i a solutio at 5C cotaiig 0.455 / of hydroxide ios, OH (aq), is.0 10 14 /. You eed to verify the [H 3 O + ] i a give solutio. You kow the [OH ] is 0.455 /. You kow the value of [H 3 O + ] you eed to verify is.0 10 14 /. Calculate a trial value of the K w usig the give values of [H 3 O + ] ad [OH ]. The [H 3 O + ] is correct if the trial value obtaied is 1.0 10 14. trial K w = [H 3 O + ][OH ] = (.0 10 14 /) (0.455 / ) = 1.0 10 14 Sice the trial value calculated for K w is the same as the accepted value, the give [H 3 O + ] is correct. If you divide the water costat by the [OH ], 0.455 /, you get a [H 3 O + ] of.0 10 14 /. The umber of sigificat digits is correct. Uit 4 Part B MHR 139
18. A solutio has a hydroium io, H 3 O + (aq), cocetratio of 0.15 / at 5C. What is the hydroxide io, OH (aq), cocetratio of this solutio? You eed to fid the fid the [OH ] for a give solutio. You kow the [H 3 O + ] is 0.15 /. costat to solve for [OH ]. OH K [H O ] w 3 1.010 0.15 14 14 6.58 10 / Multiplyig the calculated [OH ] by the give [H 3 O + ] gives the water costat, 1.0 10 14. 140 MHR Chemistry 1 Solutios Maual 978-0-07-10604-4
19. What is the hydroium io, H 3 O + (aq), cocetratio of a solutio at 5C that has a hydroxide io, OH (aq), cocetratio of 0.005 /? You eed to fid the fid the [H 3 O + (aq)] for a give solutio. You kow the [OH (aq)] is 0.005 /. costat to solve for [H 3 O + ]. [ H 3 O ] K w [O H ] 1.0 1014 0.005 4.0 10 1 / Multiplyig the calculated [OH ] by the give [H 3 O + ] gives the water costat, 1.0 10 14. Uit 4 Part B MHR 141