Question

2. (8pts) (a) The overall calculation for many volumetric analyses is given by the following equation: % Unknown = (factor)(Wt. Of Std.)(Vol. Titrant of Unknown) x 100 (Vol. Titrant Standard)(Wt. Of Unknown) Student Lucy used a wet flask as the container to weigh his standard, while student Jackie used a dry flask, whose calculated % Unknown is higher? (b) If you are asked to measure 50 mL of distilled water, which of the following items you can use? A. Beaker B. Volumetric flask C. Buret D. Graduate Cylinder (c) When you use a buret to carry out a titration, how many decimals should you record in your notebook? (d) How do you judge if a buret is still dirty?

Answer 1

a)
Lucy will weigh less standard as some of the weight will be taken by the water already present in the container. However, she will read the same weight like Jackie. But , in that manner , the strength of Lucy's standard will actually be low.So, it will take much volume of standard to complete the titration. So, the denominator of Lucy will increase.So, % unknown will be less for Lucy and higher for Jackie .

b)

Graduated Cylinder

c)

1 decimal

d)

First ,clean your burrete with normal water. Then clean it with chromic acid. Then clean it with distilled water. Finally rinse the burrete with the chemical you want to use in the burrete.

It finally makes thing clean.