Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: BabaGurGur on June 20, 2010, 04:52:02 PM
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In a flask, 0.250L of a 0.500mol/L aqueous solution of a hydrochloric acid is combined with 200ml of an aqueous solution of magnesium carbonate with a mass/volume percentage of 10%
a) Write a balanced chemical equation for the above reaction //I did this\\
= 2HCl + MgCO3 --> MgCl2 + CO2 + H20
b) Write the total ionic equation (No idea how to do this, i tried but it kept getting useless numbers)
c) Write the net ionic equation(No idea how to do this)
d) How many moles of magnesium carbonate & hydrochloric acid are available (no idea)
e) Find the number of moles of a gas produced in the above reaction between hydrochloric acid and magnesium carbonate (I did this answer is 0.625mol/L CO2)
f) Is Hydrochloric acid weak or strong acid. What is the pH of the original hydrochloric acid solution.
I've tried each and every one over and over, I did a and e but the others I can't do at all
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Try this
http://www.chemguide.co.uk/inorganic/redox/equations.html#top
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Clive: Why redox?
Baba: show what you did, we will start from there.
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Alright, For e, all I did was
0.250L * 0.500mol/L
--------------------
0.200L
= 0.125 mol
--------
0.200L
= 0.625 mol/L of gas.
The answer for a was 2HCl + MgCO3 ---> H2O + CO2 + MgCl2.
The other ones I can't complete
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e is wrong.
Let's start from the very beginning. You have 0.250 L of 0.5 M solution - how many moles of solute?
What is a net ionic reaction?
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Oh my bad, e is 0.0625, not 0.625
And I believe a net ionic is to show the things that are produced besides the acids, like H2O and CO2, they're ions?
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And I believe a net ionic is to show the things that are produced besides the acids, like H2O and CO2, they're ions?
I would love to understand what you mean.
Net ionic means that you list only things that react, and you ignore everything that is not changing (thses are called spectators).
Can you list ions present before the reaction?
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:-\ I think its H+ and CO3-2 along with H2O and CO2 ???
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Where does the CO32- comes from? What do you know about solubility of carbonates?
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I don't know much about the solubility of carbonates, and the co3 comes from the MgCO3
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MgCO3 is insoluble (well, weakly soluble), so there is no CO32-.
I bet you should know that carbonates of alkaline earth metals are weakly soluble. All of them.
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Clive: Why redox?
The title of the thread is "Net ionic equations" and that's what Jim Clarke's examples cover.
The Clarke half-equations "reveal" the transfer of electrons then the redox nature of the reactions / change in oxidation state becomes clear.
In the examples in the question above, granted, none of the species change oxidation state, but the form of the full and half-ionic equations can be based on Jim Clarkes examples
e.g. 2H+ + CO32- -> H2O + CO2
I don't see the issue.
Clive
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I don't see the issue.
Think about it this way. You are learning chemistry and you are trying to write net ionic equation for carbonate in acid. You try to read from the redox page and apply the ideas. You try to look for electron transfer - none, for changes of oxidation states - none, for half reactions - none. Conclusion - f*.* the chemistry, it doesn't make sense!
That's the issue.
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Succinctly put