Test and analysis: sodium bicarbonate reacts with hydrochloric acid to produce sodium chloride, water and carbon dioxide; According to the mass relationship diagram, when 25. 1g dilute hydrochloric acid was added, the reaction was complete, and the released gas carbon dioxide mass was 4.4g

(1) Write the chemical equation of the reaction according to the meaning of the question, calculate the mass of sodium bicarbonate in the sample by combining the mass ratio of carbon dioxide to sodium bicarbonate in the chemical equation, and then calculate according to the formula of "mass fraction of sodium bicarbonate in the sample = × 100%".

Solution: let the mass of sodium bicarbonate in the sample be x,

Sodium bicarbonate+hydrochloric acid = "sodium chloride"+carbon dioxide =+water.

84 58.5? 44?

x？ y4.4g？

84:44 = x:4.4 grams

The solution is x="8.4g "

Then the mass fraction of sodium bicarbonate in the sample = × 100%=90.3%.

(2) after the reaction is completed, the obtained solution is a sodium chloride solution, wherein the solute sodium chloride consists of sodium chloride in the original mixture and sodium chloride generated by the reaction; Therefore, when calculating the mass of solute, it is necessary to first calculate the mass of original sodium chloride and later sodium chloride, then calculate the mass of solution by mass conservation, and finally calculate it by solute mass fraction formula.

Let the mass of generated sodium chloride be y, and calculate by the above chemical equation.

58.5: 44 = y: 4.4g.

The solution is y = 5.85g.

Because the sodium chloride in the original mixture is 9.3g-8.4g = 0.9g, the mass of sodium chloride in the solution after the reaction is 0.9g+5.85g = 6.75g；;

The mass of the solution after the reaction =9.3g+25. 1g-4.4g=30g.

Therefore, when the reaction occurs completely, the mass fraction of solute in the obtained solution = × 100%=22.5%.

Answer: (1) The mass fraction of sodium bicarbonate in the sample is 90.3%; (2) When the reaction occurs, the mass fraction of the obtained solution is 22.5%.

Comments: This question is about the calculation of chemical equation and solute mass fraction. This paper mainly uses charts and reaction equation analysis to solve related problems in chemical calculation, which requires students to have strong ability to read charts and analyze data. The key to solve the problem is to calculate the mass of carbon dioxide produced when the reaction is complete by using images, and then solve the unknown demand by using related chemical reactions according to the known quantity. For the calculation of solute after reaction, it should be noted that its composition comes from the original mixture and the reaction.