1. A mixture of washing soda, Na2CO3* 10 H2O, and sodium chloride, NaCl, is heat
ID: 840257 • Letter: 1
Question
1. A mixture of washing soda, Na2CO3* 10 H2O, and sodium chloride, NaCl, is heated at 150 degree in Celcius to remove the water of hydration. If a 0.2324g sample lost 0.0654 g to give a final weight of 0.1670g. Calculate the % of washing soda in the sample (Note the 10 moles of water per mole of washing soda)??
Answer: 44.7 %
2. 0.2572g sample of 99.94% pure zinc metal was dissolved in acid and diluted to 100.0 mL in a volumetric flask. Calculate the concentration of Zn2+ in Molarity and PPM.
Answer: 0.03932 M Zn2+ /// 2.570*10^3 PPM Zn2+
3. A 3.7340 g sample of the sodium salt of EDTA was dissolved and diluted to 1.000L in a volumetric flask. This solution was used to titrate a 10.00 mL aliquot of 0.03789 M Zn2+ solution. The titration required 37.95 mL of EDTA to reach the endpoint.
a)Calculate the molarity of EDTA based on weight
b) Calculate the molarity of EDTA based on the titration
Answer: a) 0.01001 M EDTA b) 0.009984 M EDTA
4. Assuming a density of 1g/mL, express the concentration of a 0.0321 M solution of Ca ion, as: a) percent Ca, (i.e. PPH) b) mg Ca/L (PPM Ca) c)mg CaCO3/ L (PPM CaCO3)
Answer : a) 0.129 % Ca
b) 1290PPM Ca c) 3210 PPM CaCO3
5. A 100.0 mL sample of river water required 4.61 mL of 0.01619 M EDTA for titration of the calcium ion in the water. What was the concentration of the water in PPM CaCO3?
Answer) 74.7 PPM
6. A 50.00 mL sample containing both Ni and Pb ion requires 42.86 mL of 0.02026 M EDTA for titration of both metals. A second 50.00 mL sample is trated with KCN to mask the Ni ion and then titrated with 26.34 mL of the same EDTA solution. Calcualte the molarities of the Ni and Pb ions.
Answer) 0.00669 M Ni; 0.01067 M Pb
7. A 10.00mL aliquot of Mn2+ Standard solution is titrated with 0.01026 M standard EDTA solution. It takes 22.14 mL of EDTA to reach the endpoint. Calculate the concentration of Mn2+ in the standard solution
a) Molarity = 0.02272 M Mn2+
b) in Parts per million (PPM) = 1248 PPM Mn2+
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