March 29, 2024, 07:14:42 AM
Forum Rules: Read This Before Posting


Topic: reacting masses and gaseous and solution volumes  (Read 4575 times)

0 Members and 1 Guest are viewing this topic.

Offline PhilipCheney

  • New Member
  • **
  • Posts: 4
  • Mole Snacks: +0/-0
reacting masses and gaseous and solution volumes
« on: November 15, 2010, 12:20:14 AM »

I am having trouble with a question below:

Magnesium reacts with dilute hydrochloric acid:
I wrote the equation as:
 Mg(S)+ 2H+ (aq):Mg(aq)+H2(g)
If 0.720 g of magnesium is treated with 0.950 mol L -1of hydrochloric acid calculate the:
(a) The volume of hydrocholric acid needed to react with all the magnesium


What I did for a was use the mole statment and the formula n=m
                                                                                    M
and the n= V
             22.4

However I got the answer incorrect because I think I used the wrong forumals.
What are the steps to calculate the volume of HCL

Thank you

Offline Fluorine

  • Chemist
  • Full Member
  • *
  • Posts: 202
  • Mole Snacks: +22/-5
  • Gender: Male
Re: reacting masses and gaseous and solution volumes
« Reply #1 on: November 15, 2010, 12:37:42 AM »
Magnesium reacts with dilute hydrochloric acid:
I wrote the equation as:
 Mg(S)+ 2H+ (aq):Mg(aq)+H2(g)

Where the chlorine? Shouldn't the reaction of HCl with Mg be;

Mg(s) + 2HCl(aq) :rarrow: MgCl2(aq) + H2(g)
I'm still learning - always check my work/answer.

"curse Pierre Jules César Janssen!"

Offline sjb

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 3652
  • Mole Snacks: +222/-42
  • Gender: Male
Re: reacting masses and gaseous and solution volumes
« Reply #2 on: November 15, 2010, 03:58:49 AM »
I am having trouble with a question below:

Magnesium reacts with dilute hydrochloric acid:
I wrote the equation as:
 Mg(S)+ 2H+ (aq):Mg(aq)+H2(g)
If 0.720 g of magnesium is treated with 0.950 mol L -1of hydrochloric acid calculate the:
(a) The volume of hydrocholric acid needed to react with all the magnesium


What I did for a was use the mole statment and the formula n=m
                                                                                    M
and the n= V
             22.4

However I got the answer incorrect because I think I used the wrong forumals.
What are the steps to calculate the volume of HCL

Thank you

No, this formula would only be for ideal gases at stp (I think, from the limited information you have given), which an aqueous solution of hydrochloric acid is not. What equations do you know that relate solution concentration to amount of substance?

You have (correctly) identified the balanced equation for the reaction. Now, how many moles of magnesium do you have? How much HCl?

Where the chlorine? Shouldn't the reaction of HCl with Mg be;

Mg(s) + 2HCl(aq) :rarrow: MgCl2(aq) + H2(g)

Pedantically, it's chloride, but in any event it is unchanged during the reaction - have you heard of spectator ions?

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27634
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: reacting masses and gaseous and solution volumes
« Reply #3 on: November 15, 2010, 04:47:06 AM »
Mg(S)+ 2H+ (aq):Mg(aq)+H2(g)

Mg(s) + 2HCl(aq) :rarrow: MgCl2(aq) + H2(g)

"Net ionic" is the keyword here.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Fluorine

  • Chemist
  • Full Member
  • *
  • Posts: 202
  • Mole Snacks: +22/-5
  • Gender: Male
Re: reacting masses and gaseous and solution volumes
« Reply #4 on: November 15, 2010, 06:08:48 AM »
@SJB + Borek

I'm aware of spectator ions and net ionic format. When I read "equation" and "volume of HCl" I assumed the full equation was necessary. SJB I'm not sure why I said chlorine, I know better. Apologies on both fronts.
I'm still learning - always check my work/answer.

"curse Pierre Jules César Janssen!"

Sponsored Links