## A group measured the mass fraction of calcium carbonate in a limestone. 20g was taken as a nurse sample. 100g of dilute hydrochloric acid with a certain solute mass fraction was added to it

Let the mass fraction of dilute hydrochloric acid be w and the mass fraction of limestone calcium carbonate be a. according to the law of mass conservation, w = 36.5a/1000

### In order to determine the mass fraction of CaCO3 in limestone, 12.5g of limestone is added to a beaker containing 100g of dilute hydrochloric acid. The two react exactly (assuming that the impurities do not react with hydrochloric acid and do not dissolve), and the mass of substances in the beaker becomes 108.1g (1) The chemical equation of the reaction is______________________ (2) Generate CO2 gas___________________ g (3) 12.5g limestone containing CaCO3_______ g. The mass fraction of CaCO3 in limestone is________ (4) The solute in 100g dilute hydrochloric acid is _____, Its quality is ___; The solvent is ___; Its quality is_________ (5) After the complete reaction, there are insoluble impurities in the beaker. The name of the solution obtained in the beaker is ____, The mass of the resulting solution is ___, The mass of solute is ________, The mass of the solvent is__________

1、CaCO3+2HCl==CaCl2+H2O+CO2↑

2、12.5+100-108.1=4.4g

3、10g,80%

4. HCl, 7.3g. Water (H2O), 92.7g

5. Aqueous solution of calcium chloride, 105.6g, 11.1g, 94.5g

### In order to determine the mass fraction of calcium carbonate in limestone samples, the students of the research group added 100g dilute hydrochloric acid to samples of different mass respectively. The data are shown in the following table. It is known that the impurities contained in the sample are insoluble in water and do not react with hydrochloric acid Number of experiments one two three Mass of dilute hydrochloric acid (g) one hundred one hundred one hundred Mass of limestone (g) eight eighteen twenty-eight Mass of carbon dioxide (g) two point two four point four four point four Please answer the following questions as required (1) Pass carbon dioxide gas into distilled water dripping with purple litmus test solution, oscillate, and the litmus test solution changes______ Color (2) Calculate the mass fraction of calcium carbonate in the limestone sample

(1) Carbon dioxide gas is introduced into distilled water dripping with purple litmus test solution, and carbon dioxide reacts with water to form carbonic acid. The acid rendering performance of carbonic acid solution turns purple litmus test solution red; So the answer is: red (2) it can be seen from the figure that adding 8g sample to 100g dilute hydrochloric acid produces 2.2g carbon dioxide, and adding 18G sample to 100g dilute hydrochloric acid

### 100g of sodium hydroxide solution with 20% solute mass fraction was reacted with 100g of dilute hydrochloric acid exactly and completely 1 mass fraction of dilute hydrochloric acid solution 2 mass fraction of solute in the obtained solution

(1) 100g sodium hydroxide solution with 20% solute mass fraction contains 20g sodium hydroxide, 20 / 40 = 0.5mol

Sodium hydroxide reacts with hydrochloric acid one by one, requiring hydrochloric acid 0.5mol = 0.5x36.5 = 18.25g, and the mass fraction is 18.25%

(2) The solute of the obtained solution is NaCl, the amount of substance is 0.5mol, and the mass is 0.5x (23 + 35.5) = 29.25g

The mass fraction is 29.25/200 = 14.625%

### How many grams of carbon dioxide can be obtained by the reaction of 100g calcium carbonate with dilute hydrochloric acid What is the volume of these gases under standard conditions? (it is known that the density of CO2 under standard conditions is about 2.0g/l)

Let the mass of CO2 generated be X

CaCO3+2HCl=CaCl2+H2O+CO2↑

100 44

100g x

100/100=44/x

x=44g

Volume of CO2 v = m/ ρ= 44/2=22L

A: 44g carbon dioxide can be obtained by reacting 100g calcium carbonate with dilute hydrochloric acid. The volume of these gases under standard conditions is 22L

### 32.5 g of zinc can react exactly with 150 g of sulfuric acid solution. Calculation 1. What is the mass fraction of solute in this sulfuric acid solution? 2. How many grams of water is needed to dilute 100 grams of this sulfuric acid into 20% sulfuric acid?

Mass X of solute in sulfuric acid solution

Zn + H2SO4 === ZnSO4 +H2

65 98

32.5 X

X=49g

49/150≈32.7%

32.7/20%=163.5g

163.5g-100g=63.5g

Add 63.5g of water