Question

Calculations of hardness as CaCO3 in ppm and the Standard deviation and % Relative deviation. I need help step by step on how to calculate these.

Trial 1 50.00 33.52 Trial 2 Trial 3 50.00 31.92 Trial 4 Volume of water sample used (mL) Volume of EDTA titrant used (mL) Average Conc. of 50.00 32.47 EDTA (M)4 x10 Hardness as CaCOs (ppm) Average Hardness as CaCOs (ppm) Standard Deviation %Relative Standard Deviation 95% Cl

Answer 1

First, the mg of CaCO3 in the water, calculated by EDTA, is calculated:

mg CaCO3 = M EDTA * V EDTA * MM CaCO3 * 1000 = 2.42x10 ^ -3 mol / L * 0.0352 L * 100 g / mol * 1000 = 8.52 mg

Trial 2: 7.86 mg

Trial 3: 7.72 mg

We calculate the ppm of CaCO3:

ppm = mg / L = 8.52 mg / 0.05 L = 170.4 ppm

Trial 2: 157.2 ppm

Trial 3: 154.4 ppm

Average = 160.7 ppm

Standard Deviation = 8.5 ppm

% SD = SD * 100 / Ave = 8.5 * 100 / 160.7 = 5.29%

If you like the answer, please rate it in a positive way, you will help me a lot, thank you.