You wish to prepare 50.00 mL of 0.0250 M NH3 from concentrated ammonia (15.28 M)

Question

You wish to prepare 50.00 mL of 0.0250 M NH3 from concentrated ammonia (15.28 M) by serial dilution using two 50 mL volumetric flasks, a 1.00 mL pipet, and a 10.00 mL graduated pipet. One mL of concentrated ammonia is added to a 50.00 volumetric flask and it is filled to the line. What volume of this diluted solution should be added to the other volumetric flask to give the 0.0250 M NH3 solution when the flask is filled to the line?

Select one:

a. 2.05 mL

b. 2.50 mL

c. 5.00 mL

d. 0.38 mL

e. 4.09 mL

Explanation / Answer

M1V1 = M2 V2

M1=15.28 M V1 = 1 mL M2 = ? V2 = 50 ml

M2 = M1V1/V2 = 15.28*1/50 = 0.3056 M
by taking 1 ml of 15.28 M ammonia in volumetric flask and make up to the line gives 0.3056 M solution.

M3V3 = M4V4
M3 = 0.3056 M V3 = ? M4 = 0.025 V4 = 50 Ml

V3=volume of 0.3056M solution required = M4V4/M3 = 0.025*50/0.3056 = 4.09 ml

By taking 4.09 ml of 0.3056 M solution in volumetric flask and make up to the line we will get 50 ml of 0.025 M NH3 Solution.

Ans is e.4.09 ml

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