Warning: Illegal string offset 'html' in /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php on line 909

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 114

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 127

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 136

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 137

Warning: Cannot modify header information - headers already sent by (output started at /home/hsn/public_html/forum/cache/skin_cache/cacheid_1/skin_topic.php:909) in /home/hsn/public_html/forum/admin/sources/classes/output/formats/html/htmlOutput.php on line 141
Acids and Bases question - HSN forum

Jump to content


Acids and Bases question


29 replies to this topic

#1 gary

    Child Prodigy

  • Members
  • PipPipPipPipPipPip
  • 546 posts

Posted 12 April 2005 - 06:08 PM

Phosporic acid is an important chemical with many applications in industry. Some phosphoric acid is converted to sodium phosphate. This forms an alkaline solution in water and is used as a cleaning agent.

Explain fully why solutions of sodium phosphate are alkaline.

#2 bred

    Brendan

  • Moderators
  • PipPipPipPipPipPipPipPip
  • 4,215 posts
  • Location:Edinburgh
  • Interests:I have just graduated with a 2:1 in Geography [MA (Hons)] from The University of Edinburgh. I like sports: swimming, cycling, snowboarding, running, football, mountain biking and also travelling and photography.
  • Gender:Male

Posted 12 April 2005 - 06:16 PM

Phosphoric acid is a strong weak acid (pH 3) and sodium hydroxide is a very strong alkali (pH 14) so when the two products react to form sodium phosphate solution it is alkaline (14+3)/2=8.5 which renders it alkaline.
pH 3 means there is a hydrogen ion concentration of 1x10 to the -3.
pH 14 means there is a hydrogen ion concentration of 1x10 to the -14.

Edited by bred, 27 April 2005 - 09:24 PM.

Please vote for me! (Brendan Howard, 5th from bottom, only 1 vote required): http://answers.polld...m/poll/2330393/

#3 werlop

    Fully Fledged Genius

  • Moderators
  • PipPipPipPipPipPipPip
  • 1,497 posts
  • Location:Cambridge (Term Time), Bearsden (Glasgow) Non Term Time
  • Gender:Male

Posted 12 April 2005 - 08:36 PM

Are you sure phosphoric acid is a weak acid?

It is a stronger acid than acetic acid but weaker than sulfuric acid and hydrochloric acid. Does this mean it's classified as weak or strong?
Click here to visit the Bearsden Academy Website
user posted image


If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you
But make allowance for their doubting too,
If you can wait and not be tired by waiting,
Or being lied about, don't deal in lies,
Or being hated, don't give way to hating,
And yet don't look too good, nor talk too wise:
Yours is the Earth and everything that's in it,
And--which is more--you'll be a Man, my son!

#4 bred

    Brendan

  • Moderators
  • PipPipPipPipPipPipPipPip
  • 4,215 posts
  • Location:Edinburgh
  • Interests:I have just graduated with a 2:1 in Geography [MA (Hons)] from The University of Edinburgh. I like sports: swimming, cycling, snowboarding, running, football, mountain biking and also travelling and photography.
  • Gender:Male

Posted 12 April 2005 - 08:41 PM

That's a good point. Thanks for putting me right. smile.gif It is actually a strong acid with pH 3 but sodium hydroxide is even stronger as an alkali with pH 14 so the balance tips the sodium phosphate solution to the alkaline side. I don't think the question involves any more complexity than that?
Please vote for me! (Brendan Howard, 5th from bottom, only 1 vote required): http://answers.polld...m/poll/2330393/

#5 werlop

    Fully Fledged Genius

  • Moderators
  • PipPipPipPipPipPipPip
  • 1,497 posts
  • Location:Cambridge (Term Time), Bearsden (Glasgow) Non Term Time
  • Gender:Male

Posted 12 April 2005 - 08:51 PM

hmm in my advanced higher chemistry investigation i used different acids for synthesis of aspirin and phosphoric gave a yield in the region that other strong acids did, that's why i wondered.

I'm not 100% sure though. I think its sort of inbetween strong and weak.
Click here to visit the Bearsden Academy Website
user posted image


If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you
But make allowance for their doubting too,
If you can wait and not be tired by waiting,
Or being lied about, don't deal in lies,
Or being hated, don't give way to hating,
And yet don't look too good, nor talk too wise:
Yours is the Earth and everything that's in it,
And--which is more--you'll be a Man, my son!

#6 gary

    Child Prodigy

  • Members
  • PipPipPipPipPipPip
  • 546 posts

Posted 12 April 2005 - 08:54 PM

The only strong acids are:

hydrochloric acid
nitric acid
sulphuric acid

#7 werlop

    Fully Fledged Genius

  • Moderators
  • PipPipPipPipPipPipPip
  • 1,497 posts
  • Location:Cambridge (Term Time), Bearsden (Glasgow) Non Term Time
  • Gender:Male

Posted 12 April 2005 - 08:56 PM

sorry gary, you are incorrect in this case, there are many strong acids, not just those 3.
Click here to visit the Bearsden Academy Website
user posted image


If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you
But make allowance for their doubting too,
If you can wait and not be tired by waiting,
Or being lied about, don't deal in lies,
Or being hated, don't give way to hating,
And yet don't look too good, nor talk too wise:
Yours is the Earth and everything that's in it,
And--which is more--you'll be a Man, my son!

#8 gary

    Child Prodigy

  • Members
  • PipPipPipPipPipPip
  • 546 posts

Posted 12 April 2005 - 08:57 PM

Sorry I was going to edit that came out wrong.

They are the three main examples of strong acids which are used so I think they are the strongest.

#9 werlop

    Fully Fledged Genius

  • Moderators
  • PipPipPipPipPipPipPip
  • 1,497 posts
  • Location:Cambridge (Term Time), Bearsden (Glasgow) Non Term Time
  • Gender:Male

Posted 12 April 2005 - 08:57 PM

All the hydrogen halides are strong acids, as are oxyacids
of halogens such as HClO base3.gif + some others such as sulphuric and nitric.
Click here to visit the Bearsden Academy Website
user posted image


If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you
But make allowance for their doubting too,
If you can wait and not be tired by waiting,
Or being lied about, don't deal in lies,
Or being hated, don't give way to hating,
And yet don't look too good, nor talk too wise:
Yours is the Earth and everything that's in it,
And--which is more--you'll be a Man, my son!

#10 Ally

    HSN Legend

  • Moderators
  • PipPipPipPipPipPipPipPip
  • 2,912 posts
  • Interests:Just finished 1st year at uni studying medicine.
  • Gender:Male

Posted 12 April 2005 - 09:01 PM

QUOTE(gary @ Apr 12 2005, 09:54 PM)
The only strong acids are:

hydrochloric acid
nitric acid
sulphuric acid

View Post


There are many more; I think those are the ones you should be aware of for Higher.

#11 gary

    Child Prodigy

  • Members
  • PipPipPipPipPipPip
  • 546 posts

Posted 12 April 2005 - 09:06 PM

QUOTE(bred @ Apr 12 2005, 06:16 PM)
Phosphoric acid is a strong acid (pH 3) and sodium hydroxide is a very strong alkali (pH 14) so when the two products react to form sodium phosphate solution it is alkaline (14+3)/2=8.5 which renders it alkaline.
pH 3 means there is a hydrogen ion concentration of 1x10 to the -3.
pH 14 means there is a hydrogen ion concentration of 1x10 to the -14.

View Post



Would I be expected to know the first part of that for Higher, in my notes there is nothing which says this type of stuff.

#12 werlop

    Fully Fledged Genius

  • Moderators
  • PipPipPipPipPipPipPip
  • 1,497 posts
  • Location:Cambridge (Term Time), Bearsden (Glasgow) Non Term Time
  • Gender:Male

Posted 12 April 2005 - 09:07 PM

Yes, I'm afraid so.
Click here to visit the Bearsden Academy Website
user posted image


If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you
But make allowance for their doubting too,
If you can wait and not be tired by waiting,
Or being lied about, don't deal in lies,
Or being hated, don't give way to hating,
And yet don't look too good, nor talk too wise:
Yours is the Earth and everything that's in it,
And--which is more--you'll be a Man, my son!

#13 werlop

    Fully Fledged Genius

  • Moderators
  • PipPipPipPipPipPipPip
  • 1,497 posts
  • Location:Cambridge (Term Time), Bearsden (Glasgow) Non Term Time
  • Gender:Male

Posted 12 April 2005 - 09:09 PM

See http://www.hsn.uk.net/pdf/HSN13100.pdf
Click here to visit the Bearsden Academy Website
user posted image


If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you
But make allowance for their doubting too,
If you can wait and not be tired by waiting,
Or being lied about, don't deal in lies,
Or being hated, don't give way to hating,
And yet don't look too good, nor talk too wise:
Yours is the Earth and everything that's in it,
And--which is more--you'll be a Man, my son!

#14 gary

    Child Prodigy

  • Members
  • PipPipPipPipPipPip
  • 546 posts

Posted 12 April 2005 - 09:11 PM

Ethanoic Acid has ph=3 and Phosphoric acid also has a ph=3, so is the answer to the question correct?

I am getting confused.

#15 bred

    Brendan

  • Moderators
  • PipPipPipPipPipPipPipPip
  • 4,215 posts
  • Location:Edinburgh
  • Interests:I have just graduated with a 2:1 in Geography [MA (Hons)] from The University of Edinburgh. I like sports: swimming, cycling, snowboarding, running, football, mountain biking and also travelling and photography.
  • Gender:Male

Posted 12 April 2005 - 09:12 PM

Random question: Is caesium hydroxide and hydrofluoric acid the most reactive combination of acid and alkali? I imagine there would be some fireworks.
Please vote for me! (Brendan Howard, 5th from bottom, only 1 vote required): http://answers.polld...m/poll/2330393/

#16 bred

    Brendan

  • Moderators
  • PipPipPipPipPipPipPipPip
  • 4,215 posts
  • Location:Edinburgh
  • Interests:I have just graduated with a 2:1 in Geography [MA (Hons)] from The University of Edinburgh. I like sports: swimming, cycling, snowboarding, running, football, mountain biking and also travelling and photography.
  • Gender:Male

Posted 12 April 2005 - 09:12 PM

QUOTE(gary @ Apr 12 2005, 10:11 PM)
Ethanoic Acid has ph=3 and Phosphoric acid also has a ph=3, so is the answer to the question correct?

I am getting confused.

View Post


I'm not sure where ethanoic acid comes into it?
Please vote for me! (Brendan Howard, 5th from bottom, only 1 vote required): http://answers.polld...m/poll/2330393/

#17 werlop

    Fully Fledged Genius

  • Moderators
  • PipPipPipPipPipPipPip
  • 1,497 posts
  • Location:Cambridge (Term Time), Bearsden (Glasgow) Non Term Time
  • Gender:Male

Posted 12 April 2005 - 09:13 PM

QUOTE
Random question: Is caesium hydroxide and hydrofluoric acid the most reactive combination of acid and alkali? I imagine there would be some fireworks.


I think so, HF(aq) is some VERY nasty stuff.
Click here to visit the Bearsden Academy Website
user posted image


If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you
But make allowance for their doubting too,
If you can wait and not be tired by waiting,
Or being lied about, don't deal in lies,
Or being hated, don't give way to hating,
And yet don't look too good, nor talk too wise:
Yours is the Earth and everything that's in it,
And--which is more--you'll be a Man, my son!

#18 gary

    Child Prodigy

  • Members
  • PipPipPipPipPipPip
  • 546 posts

Posted 12 April 2005 - 09:14 PM

It is not in the question. Sorry.

However, Ethanoic acid has ph 3 and is stated as a weak acid, so if phosphoric acid has a ph of 3 would it not also be a weak acid.

#19 bred

    Brendan

  • Moderators
  • PipPipPipPipPipPipPipPip
  • 4,215 posts
  • Location:Edinburgh
  • Interests:I have just graduated with a 2:1 in Geography [MA (Hons)] from The University of Edinburgh. I like sports: swimming, cycling, snowboarding, running, football, mountain biking and also travelling and photography.
  • Gender:Male

Posted 12 April 2005 - 09:19 PM

Where did you read that? I think ethanoic acid has a pH of 4 to 5.
Please vote for me! (Brendan Howard, 5th from bottom, only 1 vote required): http://answers.polld...m/poll/2330393/

#20 gary

    Child Prodigy

  • Members
  • PipPipPipPipPipPip
  • 546 posts

Posted 12 April 2005 - 09:20 PM

From the link Werlop gave me:

http://www.hsn.uk.net/pdf/HSN13100.pdf





1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users