Chemical Forums

Please login or register.

Login with username, password and session length

Sponsored links

Pages: [1]   Go Down

Author Topic: Al + NaOH --> Al(OH)4 not Al(OH)3?  (Read 78607 times)

0 Members and 2 Guests are viewing this topic.

zeoblade

  • Regular Member
  • ***
  • Mole Snacks: +1/-0
  • Offline Offline
  • Posts: 88
Al + NaOH --> Al(OH)4 not Al(OH)3?
« on: February 26, 2010, 07:37:28 PM »

When reacting Al metal and NaOH(aq), I thought initially I would get the following reaction:
Al(s) + 3NaOH(aq) --> Al(OH)3(aq) + 3Na(s)

But I feel this is not correct and wondered if it should be:
2Al(s) + 2NaOH(aq) + 3H2O(l) --> 2Al(OH)4-(aq) + 2Na+(aq) + 3H2(g)

In explaining this reaction, how does hydrogen gas combine together to be evolved in this reaction?

Is there a possibility it could also be like this and why?
2Al(s) + 2NaOH(aq) + 2H2O(l)  2NaAlO2(s) + 3H2(g)
Logged

Schrödinger

  • Chemist
  • Sr. Member
  • *
  • Mole Snacks: +138/-98
  • Offline Offline
  • Gender: Male
  • Posts: 1159
Re: Al + NaOH --> Al(OH)4 not Al(OH)3?
« Reply #1 on: February 26, 2010, 10:12:43 PM »

But I feel this is not correct and wondered if it should be:
2Al(s) + 2NaOH(aq) + 3H2O(l) --> 2Al(OH)4-(aq) + 2Na+(aq) + 3H2(g)
Is the equation balanced?

Is there a possibility it could also be like this and why?
2Al(s) + 2NaOH(aq) + 2H2O(l)  2NaAlO2(s) + 3H2(g)
This one is correct. It is actually one of the commercial methods to produce H2 gas(pure), if I'm not wrong.
Logged
"Destiny is not a matter of chance; but a matter of choice. It is not a thing to be waited for; it is a thing to be achieved."
- William Jennings Bryan

Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Mole Snacks: +1562/-389
  • Offline Offline
  • Gender: Male
  • Posts: 23713
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Al + NaOH --> Al(OH)4 not Al(OH)3?
« Reply #2 on: February 26, 2010, 10:21:28 PM »

But I feel this is not correct and wondered if it should be:
2Al(s) + 2NaOH(aq) + 3H2O(l) --> 2Al(OH)4-(aq) + 2Na+(aq) + 3H2(g)
Is the equation balanced?

Is there a possibility it could also be like this and why?
2Al(s) + 2NaOH(aq) + 2H2O(l)  2NaAlO2(s) + 3H2(g)
This one is correct. It is actually one of the commercial methods to produce H2 gas(pure), if I'm not wrong.

Note: once balanced they both describe the same process, I would not call one "correct" and the other "incorrect".
Logged
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Schrödinger

  • Chemist
  • Sr. Member
  • *
  • Mole Snacks: +138/-98
  • Offline Offline
  • Gender: Male
  • Posts: 1159
Re: Al + NaOH --> Al(OH)4 not Al(OH)3?
« Reply #3 on: February 26, 2010, 10:37:55 PM »

Note: once balanced they both describe the same process, I would not call one "correct" and the other "incorrect".
But what about the aluminium hydroxide idea? Is that correct?
Logged
"Destiny is not a matter of chance; but a matter of choice. It is not a thing to be waited for; it is a thing to be achieved."
- William Jennings Bryan

zeoblade

  • Regular Member
  • ***
  • Mole Snacks: +1/-0
  • Offline Offline
  • Posts: 88
Re: Al + NaOH --> Al(OH)4 not Al(OH)3?
« Reply #4 on: February 26, 2010, 10:38:48 PM »

Al(s) + 2NaOH(aq) + 2H2O(l) --> Al(OH)4-(aq) + 2Na+(aq) + H2(g)

Sorry it should be this

2Al(s) + 2NaOH(aq) + 2H2O(l) --> 2NaAlO2(s) + 3H2(g)

So both describing the same process, how are Al(OH)4-(aq) and 2NaAlO2(s) related?
Logged

Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Mole Snacks: +1562/-389
  • Offline Offline
  • Gender: Male
  • Posts: 23713
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Al + NaOH --> Al(OH)4 not Al(OH)3?
« Reply #5 on: March 24, 2014, 04:24:02 AM »

So both describing the same process, how are Al(OH)4-(aq) and 2NaAlO2(s) related?

This is basically the same substance:

Na+ + Al(OH)4- :rarrow: NaAlO2 + 2H2O
Logged
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

bubblegumpi

  • Regular Member
  • ***
  • Mole Snacks: +1/-0
  • Offline Offline
  • Posts: 16
Re: Al + NaOH --> Al(OH)4 not Al(OH)3?
« Reply #6 on: August 09, 2017, 04:59:33 AM »

Note: once balanced they both describe the same process, I would not call one "correct" and the other "incorrect".
But what about the aluminium hydroxide idea? Is that correct?

If you think about how the energy would flow or entropy the sodium wouldn't go into solution.

First the sodium doesn't have anything to balance it out; like in the case of NaCl the chloride ions keep the sodium ions from reacting with the water.
Second if the sodium was made it would react with the water forming first sodium oxide then sodium hydroxide, which is what you started with so there would be an energy/entropy "imbalance". All reactions go to to the lowest energy state.
Logged
Pages: [1]   Go Up
 

Mitch Andre Garcia's Chemical Forums 2003-Present.

Page created in 0.265 seconds with 23 queries.