I have 2 Q in my HW I can't solve them .
the first one I did not understand it ,the second I tried but I failed



1- An aqueous solution contains NaNO3 and KSCN . The thiocyanate ion is precipitate as AgSCN by addition of AgNO3 . After an excess of the precipitating reagent has been added .

a- What is the charge on the surface of the coagulated collidal?
b- What is the source of the charge ?
c- What ions make up the counter-ion layer?





2- A 0.7406 g sample of impure magnesite MgCO3 was decomposed with HCl; the liberated CO2 was collected on calcium oxide and found to weigh 0.1881g. Calculate the percentage of magnesium in the sample.

2.
Find the number of moles of carbon dioxide. (You have mass and relative mass)

Write the equation.

You'll find that one mole of CO2 is given off when 1 mole of Mg^2+ reacts.

So, you know the amount of Mg^2+ present.

Find the mass of that amount.

Then percentage purity is

Thanks a lot. .

I did what you said and I get 14%

Yes, that's the answer! :)

I'm sorry for the first number, I haven't done that yet at school :o

Quote:

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Originally Posted by Unknown008

Yes, that's the answer! :)

I'm sorry for the first number, I haven't done that yet at school :o

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That's oK. . You did what you have to. .

Thanks again. .