An Introduction to Qualitative Analysis


Part I – Qualitative Analysis of Group 2 Elements

Mix 0.02M K2CrO4 with every Mg(NO3)2, Ca(NO3)2, Sr(NO3)2 and Ba(NO3)2 collectively. Secondly, combine 0.1M (NH4)2C2O4 as an alternative of zero.02M K2CrO4 together with the same reactants used earlier than. Thirdly, mix zero.1M Na2SO4 with these reactants. Then, combine 0.1M NaOH with the identical reactants used before once more.

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Part II – Qualitative Analysis of Selected Anions

First combine 1M HNO3 with every Na2CO3, Na2SO4, NaCl and NaI together.

Repeat these steps by putting zero.1M Ba(NO3)2 instead of 1M HNO3. Then mix 1M HNO3 for the reactants that shaped precipitates. Repeat the first step by placing zero.1M AgNO3 as a substitute of 1M HNO3. Then add 6M NH3 to those mixtures that accommodates precipitates in, and 1M HNO3 the mixtures incorporates precipitates. Using these remark, determine an unknown union.

State the id of your unknown (along with its sample number). Give the reasoning you used to reach at this conclusion.

The Unknown Z must be SO42- as a end result of it has a identical property as SO42- does. When SO42- is added to Ba(No3)2, and AgNo3, it varieties a ppt; for the unknown anion, when it’s added to Ba(No3)2, and AgNo3, it varieties a ppt as properly. When HNO3 is added to BaSO4, the ppt disappeared; for the unknown anion, when HNO3 is added to unknown, the ppt disappeared too, therefore we can
conclude that the unknown is SO42-.

Follow-Up Questions:

  1. Devise a sequence of reactions to follow (using filtering or centrifuging the place necessary to remove precipitates) to identify an unknown containing two or more cations of Group 2 elements.

The Group 2 elements are Mg, Ca, Sr, and Ba. To establish an unknown containing two or extra cations of Group 2 elements, first add CrO4 into the answer. Then we might identify them with their color. Next we add C2O4, if the ppt is fashioned,

then we all know Ca2+ is involved in the resolution. Next we add OH into the solution, if a ppt formed, that means Mg2+ is involved within the resolution.

  1. Devise a sequence of response to observe (using filtering or centrifuging where essential to remove precipitates)to identify an unknown consisting of two or extra of two or more of the anions examined in Part 2. The anions are CO32-,SO42-,Cl-,I-.To determine an unknown consisting of two or more anions in Part 2.First add HNO3 into solution. Then we could determine them with the observations. Then we add Ba(NO3)2,if ppt fashioned, then we all know that CO32-is concerned in the answer. Next we add HNO3 into the answer, if ppt fashioned, that means SO42- is involved I the answer.
  2. Why are the reagents used to check for cations often alkali metallic salts or ammonium salts rather than salts of different metals?
    The reagents used to test for cations often alkali metal salt or ammonium salts somewhat than salts of different metals as a result of the alkali metallic is soluble with most anions. It won’t form a ppt with other anions. These reagents will stop any facet reaction from occurring within the answer.
  3. Why are the reagents used to check for anions normally a nitrate of the cation that’s reacting rather than different salts of that cation?The reagents used to check for anions often a nitrate of the cation that’s reacting quite than different salts of that cation because the nitrate is soluble with almost each cation.
  4. For fast and correct identification of drugs, major research or testing laboratories now use very subtle (and costly )equipment. Find out the name of one of many instruments now used for analysis, and briefly describe its methodology of operation.

Use glass pane. When we do the lab, we make a table on the paper, then put the glass pane on the paper sheet. After that, we solely drop one or two drops of each chemical. On the glass pane. It’s easier to watch the colour of ppt as a end result of the glass is transparent and it’s also a financial means.


In this lab, we stock out precipitation test of four cations and 4 anions, and use the observations to determine two unknowns. First we combine Mg2+, Ca2+, Sr2+, Ba2+ with K2CrO4, and observed that Sr2+ and Ba2+ types a ppt. Then after we combine (NH4)2C2O4 instead of K2CrO4, we observed that the entire cations varieties a ppt aside from Mg2+. Next, we did the identical factor by utilizing Na2SO4 and NaOH as an alternative of (NH4)2C2O4 . Lastly, we examined unknown B and located that it has the identical chemical properties with Ca2+. So we conclude that the unknown substance must be Ca2+. In part II, we mix CO32-, SO42-, Cl-, and I- with HNO3 to every of the check tube and spot no ppt fashioned.

Secondly, we combine Ba(NO3)2 as a substitute of HNO3 with the anions, and we observed that CO32- and SO42- varieties a ppt. Then we add HNO3 to the ones that fashioned ppt, and the ppt disappeared. Next, we combine AgNO3 as an alternative of Ba(NO3)2 with the anions, and observed ppt shaped with all the anions apart from SO42-. After that, we added HNO3 and NH3 separately to the anions and we observed no change in SO42-, however the precipitates that formed in CO32-, Cl-, and I- disappeared. And there’s a ppt shaped when NH3 is added to SO42-, and the other ones’ precipitates turns to a lighter ppt. By using these observations, we discovered the unknown ion accommodates the identical chemical properties as SO42-.

And if two ions are soluble to one another, there shall be no ppt fashioned. If two ions usually are not soluble to each other, there might be a ppt shaped.

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