Devise a method (two-step serial dilution) similar to that in the previous quest

Question

Devise a method (two-step serial dilution) similar to that in the previous question to make 100.00 mL of 0.025 M NH3 (ammonia), from concentrated ammonia, which has a concentration of 15.28 M. 8. Calculate the masses of the solids you must measure out to prepare 100 mL each of 0.025 M KNO3, 0.025 M CuSO4, 0.025 M Ca(NO3)2, 0.025 M Al(NO3)3, and 0.025 M KCl. (Note that some of these salts are hydrates; their formulas are: Ca(NO3)2. 4H2O, Al(NO3)3. 9H2O, and the waters of hydration when calculating the formula

Explanation / Answer

Answer

7. Pippette out 1 mL from the 15.28M and dilute it to 100mL in a Standard Measuring Flask. The concentration of this solution is 0.1528M.

100 mL of 0.025M solution contains 0.0025 moles of NH3. Pippette out (0.0025/0.1528)*1000 = 16.36 mL from the SMF and dilute it to 100mL in another SMF.

8. Salt Mass (for 100mL of 0.025M), mg

KNO3 252.758

Cu(SO4).5H2O 624.213

Ca(NO3)2.4H2O 590.375

Al(NO3)3.9H2O 937.835

KCl 186.375

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