Two chemistry questions calculation questions of acid base salts

1.Let the mass x of the solute in the original dilute sulfuric acid

The mass of hydrogen gas generated is calculated by the chemical equation as (2 98) x the amount of solid (mass of metal + mass of sulfuric acid solute - mass of hydrogen generated) and an equation is listed

20g+x-(2/98)x=

The solution is : x=, then the mass fraction of the solute in the dilute sulfuric acid is: (

Choose B2Let the mass of sodium hydroxide solution be M, then the mass of sodium hydroxide is 10% M, and the HCl mass X is set to generate NaOH mass Y

hcl +naoh =nacl +h2o

x 10%m y

Columnar calculation: x=(, y=(

Finally, the total mass of NaCl solution is: Y (

The mass of HCl solution used up is:

So the mass fraction of solutes in hydrochloric acid is:

x Calculation is not guaranteed to be all right, I love sloppiness, you can calculate it yourself.

1.Let the mass of sulfuric acid be x grams.

then SO4-2 H2SO4

96 x = grams.

So h2SO4%=

2.Extremely suspicious that you have omitted a piece of data If so, please add. I'll be able to answer).

Example: (Beijing Fengtai District High School Entrance Examination Mock Questions).

13g of soda ash sample containing a small amount of sodium chloride was put into a certain amount of hydrochloric acid solution, and 141g of solution with a solute mass fraction of 10% was obtained after a complete reaction. Calculation: Purity of the original soda ash sample.

Analysis: The main component of the soda ash sample is Na2CO3, which reacts with hydrochloric acid to form NaCl and H2O and CO2. The inscription can be represented by a diagram as:

na2co3 + 2hcl = 2nacl+h2o+co2

The known data in the problem are mixtures, can not be directly substituted into the chemical equation calculation, from the diagram is not difficult to see, the original soda ash sample in the NaCl is an intermediate quantity, if its mass is assumed, it can be expressed in the chemical equation Na2CO3 and NaCl mass, and then list the proportional formula, the problem is solved.

Solution: Let the mass of NaCl in the original soda ash sample be X, and the total mass of solute NaCl in the solution after the reaction is: 141g 10%=

na2co3 + 2hcl = 2nacl+h2o+co2

106/ 13g－x =117 /

General solution: 106 (

117x－106x=1521g－

x = easy method: use the proportional properties of proportionality to directly reduce the original proportional formula to:

106/ 13g－x =117 / =(117-106)/(

It can be seen that the numerator and the denominator are 10 times related, and it can be obtained: 13g x=

The mass of x= Na2CO3 is: 13g.

The purity of the primary soda ash sample was;

A: The purity of the original soda ash sample is about:

Acid-base salts? If you want to make good use of the acid-base salt precipitation table, reasoning and judgment depend on it. As for calculations, the calculation problems in junior high school chemistry are very simple, mainly about the calculation of solutions and the calculation of chemical equations.

Needless to say, the calculation of the chemical equation finds the known and unknown quantities, and the relative atomic mass ratio is equal to the actual mass ratio mass, and that's it.

Learning can't be done quickly, and if it can be done quickly, then learning is too easy. The student and the questioner themselves are a game, what you are easy to learn, I generally don't take the test, and what I want to take is often something you are not familiar with. Therefore, it is only in normal times to cope with the high school entrance examination.

Training institutions like to play the fast brand, and that's just for the money.

It is recommended to do more questions in the past year exams and master more methods of problem solving. **Class, graphic class, do more practice.

This is to test my usual accumulation, and I'm also very bad at chemistry.

The main thing is the application of formulas and the like, and if you look at the formulas before the exam, you can improve a large part of your scores.

1: Set: When preparing dilute hydrochloric acid, V ml of concentrated hydrochloric acid with a solute mass fraction of 37% was measured according to the equal mass of hydrochloric acid in the solution before and after.

Solution: V 2: The HCl solute in the 200g solution is 200 5%=10g, then the HCl solute in the 73g solution is 73 5%=

hcl+naoh=nacl+h2o

The solution is m=4g

4 A: The mass fraction of sodium hydroxide contained in sewage is:

Establish. When dilute hydrochloric acid is configured, V ml of concentrated hydrochloric acid with a solute mass fraction of 37% is measured 200*5%=v*

Solution v=23ml

hcl+naoh=nacl+h2o

73*5%--x

Solution x=4g

Therefore, the mass fraction of sodium hydroxide contained in sewage is 4 80 = 5%.

Let the mass of KCl in the sample be X, and the mass of the reaction to form Kno3 is Y.

kcl+agno3=kno3+agcl↓

101x yx=

y = the mass of potassium nitrate in the sample is.

The quality score is:

The mass of the solute after the reaction is.

The mass of the solution is 10+

The mass fraction of the solute is.

Answer: (1) The mass fraction of potassium nitrate in the sample is:

2) The mass fraction of the solute in the solution obtained after the reaction is:

kcl+agno3==agcl↓+kno3101

x yx=y=(1) The mass fraction of potassium nitrate in the sample (

2) The mass fraction of the solute in the solution obtained after the reaction (

kcl+agno3=agcl + kno3

101x= y= mass fraction of potassium nitrate in the solution obtained by the reaction.

The 4th and 5th remaining solid masses are.

The description is impurities, then the quality of the limestone is.

Limestone is caco3

caco3+2hcl---cacl2 +h2o +co2x=

The total weight of the solution is 2g+

How to find the solvent quality of calcium chloride?

After the reaction, everything is liquid except for the impurities, which are solid, so it is enough to subtract the impurities from the added mass.

First use the equation to find the quality of water, and then use calcium chloride to remove calcium chloride and add water by 100%.

caco3+2hcl==cacl2+co2+h2om m

Find m= m=

Now the key is to demand the quality of the solution; We noticed that the CO2 in the product is removed because the gas runs away, and the other substances are still in the solution, and of course the impurities are filtered, so we know that the mass of the solution is.

The mass fraction of calcium chloride is:

The resulting calcium chloride and carbon dioxide gas are found from grams of calcium carbonate, and then the total mass of the solution after the reaction is calculated according to the conservation of mass. If the quality of the effluent is required in this question, it is also possible, that is, the water in the original dilute hydrochloric acid and the water generated. But you must not forget that dilute hydrochloric acid is in excess, and also take them into account in solution.

Therefore, calculating the mass fraction of a solute does not necessarily require the mass of the solvent, sometimes only the mass of the solute and the solution are required.

1) The solute mass is m(Naoh)=50 8%=4g

2) Product: m(Na2SO4)=4 40 (23 2+96)=

The ball gradually swells.

There are two possibilities.

1 The temperature increases, and the heat expands.

2 Low external air pressure Large internal air pressure.

Obviously, the second does not satisfy ABCD

The first one has an SO2 that can react with NaOH to release heat, so B is chosen

Let the metal be r, and r in its compound be +2 valence.

r+h2so4=rso4+h2

r 213g 1g

Column proportions, solved.

r=26 i.e., the average relative atomic mass of the metal mixture is 26.

According to the principle of averages, one is greater than 26 and the other is less than 26.

However, due to the fact that the assumptions are inconsistent with the actual situation of AL, when considering aluminum, it needs to be converted, 27*2 3=18.

So the answer is a.

1. The average relative atomic mass of this mixed metal = 13 * 2 1 = 26

Find two metals that are converted into +2 valent metals with relative atomic masses on both sides of 26. Principle of averaging.

Option 1. (Al is a 3-valent metal, and the relative atomic mass = 18 after being converted into a 2-valent metal).