Question

Which of these solutions is the most basic?

Your answer:
[OH-] = 4.3 x 10-9 M
[OH-] = 2.8 x 10-11 M
[OH-] = 6.7 x 10-10 M
[OH-] = 1.0 x 10-5 M

Answer 1

Note the rule

• pOH=-log[OH-]

And we can find the answer through logarithm rules basic

• loga^b=bloga

So

• -log10^-n=n

Higher the n higher the pOH

But

• pH=14-pOH
• Lesses pOH=Higher pH i.e basic High

As we can see

Option D has least n (5)

Hence D is more basic

Answer 2

Question↷

Which of these solutions is the most basic?

[OH-] = 4.3 x 10-9 M

[OH-] = 2.8 x 10-11 M

[OH-] = 6.7 x 10-10 M

[OH-] = 1.0 x 10-5 M

Answer↷

• [OH-] = 1.0 x 10-5 M ✓

Solution↷

[OH-] = 4.3 x 10-9 M

• [OH-] = 4.3 x 10^-9 M
• pOH = - log [OH^1-]
• pOH = - log [4.3 x 10^-9]
• pOH = 8.36
• pH = 14- 8.36
• pH = 5.64

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[OH-] = 2.8 x 10-11 M

• [OH-] = 2.8 x 10^-11 M
• pOH = - log [OH^1-]
• pOH = - log [2.8 x 10^-11 ]
• pOH = 10.55
• pH = 14-10.55
• pH = 3.45

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[OH-] = 6.7 x 10-10 M

• [OH-] = 6.7 x 10^-10 M
• pOH = - log [OH^1-]
• pOH = - log [6.7 x 10^-10]
• pOH = 9.17
• pH = 14-9.17
• pH = 4.83

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[OH-] = 1.0 x 10-5 M

• [OH-] = 1.0 x 10-5 M
• pOH = - log [OH^1-]
• pOH = - log [1.0 x 10^-5 ]
• pOH = 5
• pH = 14-5
• pH = 9

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we know that , the solution with pH > 7 is termed as basic and more the pH ,more the basicity, hence ,the solution with the highest pH would be the strongest base out of these all which is

[OH-] = 1.0 x 10-5 M with pH = 9

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