Dimethyl glyoxime gives a red precipitate with Ni2+, which is use

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 Multiple Choice QuestionsMultiple Choice Questions

641.

For a phase change

H2O(l)   0°C, 1 bar  H2O(s)

  • G = 0

  • H = 0

  • S =0

  • U = 0


642.

F2 formed by reacting K2MnF6 with

  • SbF5

  • MnF3

  • KSbF6

  • MnF4


643.

Which among the following is the strongest acid ?

  • HF

  • HCl

  • HBr

  • HI


644.

When 10 mL of 0.1 M acetic acid (pK= 5.0) is titrated against 10 ml of 0.1 M ammonia solution (pK= 5.0), the equivalence point occurs at pH

  • 5.0

  • 6.0

  • 7.0

  • 9.0


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645.

For reaction, 2NOCl (g) 2NO (g) + Cl2 (g), Kc at 427°C is 3 × 10-6 L mol-1. The value of Kp is nearly

  • 7.50 × 10-5

  • 2.50 × 10-5

  • 2.50 × 10-4

  • 1.75 × 10-4


646.

For the chemical equilibrium,

CaCO3(s) CaO(s) + CO2(g)

Hr° can be determined from which one of the following plots?


647.

pH of a solution of 10 mL 1N sodium acetate and 50 mL 2N acetic acid (Ka = 1.8 x 10-5), is approximately :

  • 4

  • 5

  • 6

  • 7


648.

The pH is less than 7, of the solution of :

  • FeCl3

  • NaCN

  • NaOH

  • NaCl


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649.

Dimethyl glyoxime gives a red precipitate with Ni2+, which is used for its detection. To get this precipitate readily the best pH range is

  • < 1

  • 2-3

  • 3- 4

  • 9- 11


D.

9- 11

Nickel(II) forms a precipitate with the organic compound dimethylglyoxime, C4H6(NOH)2. The formation of the red chelate occurs quantitatively in a solution in which the pH is buffered in the range of 5 to 9. The chelation reaction that occurs is illustrated below.

The reaction is performed in a solution buffered by either an ammonia or citrate buffer to prevent the pH of the solution from falling below 5. If the pH does become too low the equilibrium of the above reaction favors the formation of nickel(II) ion, causing the dissolution of Ni(DMG)2 back into the mother liquor.


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650.

The values of Ksp for CuS, Ag2S and HgS are 10-31, 1042, 10-54 respectively. The correct order of their solubility in water is :

  • AgS > HgS > CuS

  • HgS > Cus > Ag2S

  • HgS > Ag2S > Cus

  • Ag2S > CuS > HgS


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