Sapling Week 2 #7

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Agustina Santa Cruz 2F
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Sapling Week 2 #7

Postby Agustina Santa Cruz 2F » Sun Jan 24, 2021 8:29 pm

HClO is a weak acid ( Ka=4.0×10−8 ) and so the salt NaClO acts as a weak base. What is the pH of a solution that is 0.024 M in NaClO at 25 °C?

Why does the ICE table only include ClO- and HClO and OH-. What happened to the NaClO?

805295074
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Re: Sapling Week 2 #7

Postby 805295074 » Sun Jan 24, 2021 8:33 pm

They want to make it clear for us that mixing water and ClO- gives an conjugate acid and base.

Ayesha Aslam-Mir 3C
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Re: Sapling Week 2 #7

Postby Ayesha Aslam-Mir 3C » Sun Jan 24, 2021 8:34 pm

Hello! The ice table considers that NaClO in water dissociates into Na+ and ClO-. Since Na+ cannot form a new compound NaOh in water (bc NaOH strong base, therefore it is considered a "spectator ion"), next we see ClO- ions in water. (ClO- aq). Since these equations are all balanced with one mol of each, we can therefore conclude 0.024 M NaClO will give us 0.024 M ClO- in water that will create HClO and OH-.

Nan_Guan_1L
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Re: Sapling Week 2 #7

Postby Nan_Guan_1L » Sun Jan 24, 2021 8:39 pm

I also faced some difficulties while answering this question. What should we consider as included in the solution in NaClO? I'm confused by the wording of this question.

Sarah Hernandez 1F
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Re: Sapling Week 2 #7

Postby Sarah Hernandez 1F » Sun Jan 24, 2021 8:50 pm

Nan_Guan_1L wrote:I also faced some difficulties while answering this question. What should we consider as included in the solution in NaClO? I'm confused by the wording of this question.

The way I understand it is that the solution in NaClO includes the NaClO and H20, however as the person above mentioned the NaClO automatically dissociates into Na+ and ClO-, so the given molarity for NaClO is the same for the ClO- and you have to consider the chemical reaction occurring in the solution. That means everything there, including the HClO and OH- are included in the solution. I hope this helps!

rhettfarmer-3H
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Re: Sapling Week 2 #7

Postby rhettfarmer-3H » Sun Jan 24, 2021 9:40 pm

I also had a hard time answering this but now I think the way I understood it was that Na+ does not affect the ph of the solution so it is not mentioned in the whole of the systematic equation. Furthermore, Na dissolves in water and does not interact with water to create rippling change.

Rachael Cohen 3G
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Re: Sapling Week 2 #7

Postby Rachael Cohen 3G » Sun Jan 24, 2021 9:45 pm

I would treat this kind of question the same as any other weak acid/base question. ClO- is a weak base, so the formula we're looking at is in the form B + H2O <-> BH+ + OH-. The base is ClO-, and BH+ is HClO+. Hope this helps!

Griffin G
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Re: Sapling Week 2 #7

Postby Griffin G » Sun Jan 24, 2021 11:09 pm

Na+ doesn't affect the pH.

Adrienne Chan 1G
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Re: Sapling Week 2 #7

Postby Adrienne Chan 1G » Sun Jan 24, 2021 11:21 pm

Because Na+ is part of a strong base (NaOH), it does not affect the pH and can be ignored.


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