(1) memorize common instruments and their uses, and get the answer. The name of chart a is measuring cylinder; The name of picture b is glass rod;

(2) The function of glass rod stirring in operation ③ is to accelerate the dissolution of raw salt;

(3) In the evaporation operation, the liquid is heated evenly by the agitation of the glass rod, so as to prevent droplets or crystals from splashing due to local overheating.

(4) glass rod should be used for drainage during filtration;

(5) The experimental operation sequence of crude salt purification and yield calculation is: taking medicine, weighing medicine, putting medicine in beaker, adding water, dissolving, filtering and evaporating.

(6) In operation ④, when more solids are observed, the heating is stopped.

Experiment 2: (1) The mass of sodium chloride should be 50g×5% = 2.5g；; The required volume of water is 50g-2.5g=47.5g, and the volume is 47.5g 1g/mL =47.5mL, so it is necessary to choose a 50mL measuring cylinder.

(2) When the sodium chloride solid is still impure, the mass of sodium chloride will decrease, resulting in a small solute mass fraction;

When weighing, the position of weight and refined salt is reversed, which will reduce the quality of sodium chloride and lead to a small solute mass fraction;

When measuring water, checking readings will make more water measured, resulting in smaller solute mass fraction;

Due to the homogeneity of the solution, a small amount of solution overflowed during bottling, which had no effect on the solute mass fraction.

So the answer is: Experiment 1: (1) measuring cylinder; Glass rod;

(2) accelerating the dissolution of raw salt;

(3) prevent droplets or crystals from splashing due to local overheating;

(4) glass rod drainage is not used;

(5)①⑤②③⑥④

(6) More solids appear

Experiment 2: (1) 2.5; 47.5mL50mL

(2)①②③