REPORT No. 8 (QUESTIONS/ANSWERS) Answer in complete sentences 1) Can the pH pape
ID: 1035092 • Letter: R
Question
REPORT No. 8 (QUESTIONS/ANSWERS) Answer in complete sentences 1) Can the pH paper distinguish between pH 7 and pH 9 solutions? Can it distinguish between pH 12 and pH 14 solutions? Why or why not 2) The copper(II) ion is acidic whereas the acetate ion is basic. However, copper acetate is acidic. Without doing any calculations how could you have predicted that Cu(OAc)2 solutions should be acidic? Note: you do require the data on page 109 3) Is it possible to conclude whether an acid is weak or strong simply by measuring the pl? of its solution? Explain why or why not.Explanation / Answer
1) The answer is tricky as it depends on what ph paper you use. High quality pH papers can give individual colors for each change in pH making it possible to distinguish between any pH. However, in most cases, we can answer as:
Its easily possible to identify between pH 7 and 9. This is because pH 7 is neutal, so we have no color change , but pH 9 is basic, so paper provides obivious color change.
Distinguishing between pH 12 and 14 is not possible . This is because both pH shows highly basic solutions and pH paper shows almost same color change for both solutions.
2) You have not provided required data for a precise answer. Still, i can elaborate. Copper hydroxide and acetic acid react forming copper acetate. Both base and acid are weak. Hence , we need to interpret the dissociation values of base and acid from tables. The pK values of calcium hydroxide and acetic acid are 2.5 and 4.75 respectively, approx. Hence, copperhydroxide dissociates more , making solution more acidic.
3) pH is the measure of H + ions and by strong acid, we mean more H+ ions. Hence, pH can tell us if a solution is a strong acid solution or not. But pH alone cannot determine if the acid itself is strong or weak. Lets take 100 moles of weak acid ( citric acid) in 1 L solution and 1 mole strong acid ( HCl) in another 1 L solution. Of course, the pH value of weak acid will be more as the concentration of acid is more. This show that 100 mole citric acid solution is stronger than 1 mole HCl solution, but this doesn't mean that Citric acid is stronger acid than HCl
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