Question

post lab questions?

2. The instructions for Solution IV describe the preparation of a buffer solution. a. Calculate the pH of this buffer solution if it has an equal concentration of NHs and NH4 b. Does this solution buffer in the acidic, basic, or nearly neutral pH range? Explain. c. Explain why it is necessary to provide a buffer solution at this point in the procedure. Solution IV Add 2 drops NH.CI solution and check the pH of the solution with litmus paper acidic add 6 M NHOH until solution is basi If basic add no NHOH; if c. Add 3 drops ammonium carbonate (NH) COs. Heat for a few minutes while stirring. Centrifuge. (Note: if no precipitate forms in your unknown, then there is no need to centrifuge; proceed to step B2.) Add 1 more drop (NH4 CO, to test for complete precipitation. Centrifuge. Decant the supernatant into a tube labeled known Mg" for the known solution or 'unknown Mg for the wn solution. The precipitate is most likely Caco, (but additional tests will be performed to be sure) Precipitate IV.a CaCOs Wash the ppt. with H:O, cfg. and discard washings. Add 3-4 drops 6 M HC HsO: and stir to dissolve. Make slightly basic with 6 M NH OH and add 2 drops ammonium oxalate (NH) C204 Formation of CaC204 ppt indicates Ca2 is present. Cfg. and discard soln. Add a few drops 6M HCI and stir to dissolve the ppt. Perform a flame test using the resulting soln. A red-orange flame presence of Mg Solution IV.b Mg First remove a few drops & perform a flame test. Visually adjust the volume of the soln. to 0.5 mL and make basic with 6 M NH OH. Add 3 drops more 6 M NH OH, then add 3 drops sodium hydrogen phosphate (Na HPO4). Stir and allow to stand for 5-10 min. (ppt. may form slowly). The formation of a ppt. (MgNH4PO4) confirms the confirms the presence of Ca2 pre presen

Answer 1

CNH3 prt- 14-4.75 = 9.2.5 t aud Cat as wrbowts taker plave