1. If 20.00 mL of stock solution with concentration of 50.00 mgL-1 is diluted to

Question

1. If 20.00 mL of stock solution with concentration of 50.00 mgL-1 is diluted to 100.00 mL, the dilute soluion will have a concentration of

Select one:

a. 10.00 mg per L.

b. 25.00 mg per L.

c. 5.00 mg per L.

d. 20.00 mg per L.

2, The nitrite ion is represented as Select one:

a. NO2-

b. NO32-

c. NO22-

d. NO3-

3. The pH of a 0.001M HCl solution would be approximately

Select one:

a. 1

b. 3

c. 6

d. 11

   4.     In the Thin Layer Chromatography experiment, the stationary phase was

Select one:

a. the solvent

b. the white coating on the slide

c. the ninhydrin spray

d. the samples that were spotted on the slide

5.      When 1 drop of universal indicator was added to a solution, the colour of the solution was observed to be blue. The solution could be described as being

Select one:

a. neutral

b. a buffer

c. basic

d. acidic

6.When HCl (aq) is exactly neutralised by NaOH(aq), the hydrogen ion concentration in the resulting mixture is

Select one:

a. always equal to the concetration of the hydroxide ions.

b. always less than the concentration of the hydroxide ions.

c. sometimes equal to the concentration of the hydroxide ions.

d. always greater than the concentration of the hydroxide ions.

Explanation / Answer

1) a , THE DILUTION IS 5 TIMES AND SO THE CONCENTRATION DECREASES 5 TIMES. [20*50/100 = 10]

2)a , NO2- NITRITE ION IS HAVING UNI NEGATIVE CHARGE,

NO3- , THIS NITRATE ION

3) b,

pH = - LOG[H+ ], pH IS DEFINED AS NEGAIVE LOGARTHIM OF HYDROGEN ION CONCENTRATION.

GIVEN [H+ ] = 0.001 = 10 -3   SO LOGARTHIM VALUE OF GIVEN HYDROGEN ION GIVES pH VALUE OF 3.

4) b, white coating on the slide, this white coating is alumina(aluminium oxide)

5) c, if universal indicator gives blue its pH value falls in the region 8 to 10 , so it is basic.

6) a, it is neutralization reaction. 1 mole of HCl = 1mole of NaOH ( this is exact )

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