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November 01, 2025, 12:31:34 pm
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Author Topic: calculationss  (Read 1491 times)  Share 

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mandy

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calculationss
« on: August 30, 2009, 11:57:55 am »
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0.0010M HNO3(aq)

a. calculate the concentration of H3O+ ions

b. calculate the concentration of OH- ions

c. calculate the pH

How would I start this qn off..
« Last Edit: August 30, 2009, 12:02:38 pm by mandy »
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d0minicz

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Re: calculationss
« Reply #1 on: August 30, 2009, 12:03:21 pm »
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a)


b) Assuming at 25 degrees celcius



c)
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mandy

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Re: calculationss
« Reply #2 on: August 30, 2009, 12:10:14 pm »
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Quote from: d0minicz on August 30, 2009, 12:03:21 pm
a)


b) Assuming at 25 degrees celcius



c)



in part (a), how do I know that the concentration of hydronium ions is equal to the concentration of the solution? Am i meant to write some sort of equation and see a ratio :S
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d0minicz

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Re: calculationss
« Reply #3 on: August 30, 2009, 12:18:23 pm »
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Umm (theyre the same thing)
you see in theres 1 hydrogen
so the is the same as
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mandy

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Re: calculationss
« Reply #4 on: August 30, 2009, 12:27:52 pm »
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okay, thanks :)
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mandy

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Re: calculationss
« Reply #5 on: August 30, 2009, 09:24:50 pm »
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i keep doing this qn over and over, and keep getting it wrong.

Calculate the concentration of H3O+ ions, the concentration of OH- ions and the pH of:
500mL solution which contains 0.50g dissolved KOH
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hyperblade01

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Re: calculationss
« Reply #6 on: August 30, 2009, 09:51:00 pm »
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Find the mol of KOH n = m/M

n(KOH) = n(OH-)

Find the concentration of OH using c = n/v

Find the concentration of [H3O] using [H3O+] = 10^-14/[OH-]

Find the pH using pH = -log[H3O+]
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sir0004

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Re: calculationss
« Reply #7 on: August 30, 2009, 09:51:16 pm »
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First find the number of moles of KOH. n = m/M= 8.91 * 10-3
Now write the equation: KOH---OH- + K+
Hence, same number of moles of KOH and OH-
Now find the conc of OH-. c= n/v= 0.0178M
Use the formula which states that the concentration of OH- multiplied by concentration of H30+ equal to 10-14 to find that that the conc of H30+ is 5.61-13.
Now use –log (conc of H30+) to get the pH of 12.3
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mandy

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Re: calculationss
« Reply #8 on: August 30, 2009, 10:02:51 pm »
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when i put the value of [H3O+] into the -log formula, the answer isnt 12.3, but is 4.25 :S
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d0minicz

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Re: calculationss
« Reply #9 on: August 30, 2009, 10:04:07 pm »
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i think you put the OH one in
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mandy

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Re: calculationss
« Reply #10 on: August 30, 2009, 10:15:06 pm »
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oh, i've got the answer now. thank you <3
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ed_saifa

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Re: calculationss
« Reply #11 on: August 30, 2009, 10:50:11 pm »
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This formula may prove useful at times
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Mao

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Re: calculationss
« Reply #12 on: August 30, 2009, 11:58:41 pm »
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Quote from: ed_saifa on August 30, 2009, 10:50:11 pm

This formula may prove useful at times

be careful, that applies only at 25 degrees Celsius.
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