Titration Curve

TheGreenGiant

Hey peoples, really stuck on this dang question as I'm really not sure where to start. I know I need to plot pH vs the volume of AgNO3 I just don't know what calculations I need to preform for me to get to where I can calculate the pH. Any guidence is much appreciated The question is:

Consider the precipitation titration of 25ml of a solution that is 0.10 M in KI and a solution that is 0.05 M in AgNO3. Calculate the concentration of I^- and thus Ag^+ in solution after the addition of a 10ml, 20ml, 45ml, 50ml, 55ml and 60ml of the AgNO3 solution.

Using this data, construct a titration curve, plotting pAg against volume of AgNO3 solution added.
Ksp for AgI= 8.3*10^-17

Reenakjr

Hi Green,

The amount of halogen in a compound is estimated by Carius method.

Calculations:

Let, the mass of the compound taken = W g
Mass of AgX formed = W1 g

From stoichiometry,
Ag = X
1 mol 1 mol
1 molecular mass 1 atomic mass

Therefore,

Mass of halogen in W1 g of AgX = (Atomic mass of X / Molecular mass of AgX) W1

% of Halogen = (Mass of halogen in W1 g of AgX / Mass of compound taken) 100

= (Atomic mass of X * W1) / Molecular mass of AgX

• These precipitation reactions can be represented by the following equations,

where X = Cl, Br or I:
Silver nitrate + potassium iodide →silver iodide + potassium nitrate.

AgNO3(aq) + KI(aq) → AgI(s) + KNO3(aq)
The tests above are made in the presence of dilute nitric acid to remove any carbonate or sulfite ions which may be present.
The ionic equation is Ag+(aq) + I-(aq) → AgI(s)

• Silver iodide (AgI) is an inorganic compound. This yellow photosensitive solid is used in photography, as an antiseptic in medicine, and in rainmaking or cloud seeding. Silver iodide is highly insoluble in water.

• AgI photo-decompose to the metal, as evidence by a grayish color on exposed samples.

Best wishes...

cianl1

Ignore the above post. The Carius method has nothing to do with what your question was asking for.

Use the equations n = m/Mr and M = n x 1000/V

where n = no. of moles of substance
M = concentration
V = volume
and Mr = molecular mass

Calculate the moles of silver nitrate then calculate concentration at the various volumes.

Remember pH = -log[Ag]. Plot the resulting values against the corresponding volumes of AgNO3.

TheGreenGiant

just got your messages there. Thanks for replying. I actually worked it out over the weekend. Its not too bad, just long winded lol Have the chemistry exam now in the morning so I hope it goes well!

Thanks again