Question

5. What is the pH of a solution of 0.0100 M HCl dissolved in 0.01334 M potassium carbonate when taking solution activity into account?

6. What would be the uncertainty of a 0.5000 M solution of Fe3+ prepared from solid iron (III) sulfate with a ±0.01 g balance and a 250.00 ±0.08 mL volumetric flask?

i need the work for both questions by 12:15pm 2/25/16 PLEASE!

Answer 1

Question 5:

Overall reaction:

2HCl + K₂CO₃ ---------> 2KCl + CO₂ + H₂O

Assuming we have 1 L of both solutions, and that we are having a reaction between a weak base and a strong acid. The moles of HCl would be 2 moles of K₂CO₃, so the OH concentration would be:

[OH^-] = 2M_bV_b - M_aV_a / V_a + V_b

[OH^-] = 2(0.01334) - 0.01334 / 1+1

[OH^-] = 0.00834 M

pOH = -log(0.00834) = 2.08

pH = 14-2.08

pH = 11.92

Question 6.

The molecular weight of Fe is (55.845 0.002) g/mol

and we have the volume, let's calculate first the mass:

m = 0.5000 mol/L * 0.250 L * 55.845 g/mol = 6.98 0.01 g

then the uncertainty it would be:

dM = (0.01/6.98) + (0.00008/0.250) + (0.002/55.845) = 0.001788

0.001788 * 0.5 = 0.00089

M = (0.5000 0.0009) M

Hope this helps