Grade 9 Chemistry Calculation Questions Hurry, Hurry, Hurry .

R2O3+3H2SO4==R2(SO4)3+3H2O4GThe oxide of a certain positive trivalent metal R reacts exactly completely with 21g of dilute sulfuric acid, and the total mass of the solution after the reaction is 25g after the reaction is obtained by mass conservation.

The solute mass fraction of the solution obtained after the reaction is 40 100, so the mass of R2(SO4)3 is 10g.

r2o3+3h2so4==r2(so4)3+3h2o2r+48 2r+288

4g 10g

2r+48/4==2r+288/10

The solution is r=56

r2o3+3h2so4==r2(so4)3+3h2o4g

So the solute mass fraction of dilute sulfuric acid is.

Solution: R2O3 3H2SO4 R2(SO4)3 3H2O is obtained by the law of conservation of mass, and the total mass of the solution after the reaction is 25g, so the mass of R2(SO4)3 is 25 40 10g.

R2O3 3H2SO4 R2(SO4)3 3H2O M (Mass difference between R2O3 and R2(SO4)3).

2r＋48 294 2r＋288 240

4g 10g 6g

R 56 solute mass fraction of dilute sulfuric acid

t, 15g of calcium carbonate powder is reacted exactly completely with a certain amount of dilute hydrochloric acid. After the reaction is a saturated solution with a mass fraction of 25% solute. (1) What is the mass of the solution obtained after the reaction, and (2) The mass fraction of the solute in dilute hydrochloric acid.

Solution: Supplied...

caco3+2hcl=cacl2+h2o+co2↑15g z x y

Column proportion, solved, x= y= z=

The mass of the solution obtained after the reaction =

Mass fraction of solutes in dilute hydrochloric acid =

Answer:..

a+3b=2c+2d

9k 33k

x9k/33k=

x = mass of product c.

In this reaction, the mass ratio of reactant B and product C :1 produces oxygen and the mass is.

2h2o2= mno2= 2h2o+ o2↑68 32

x68/32=x/

x = the mass of manganese dioxide in the mixture is.

The mass of oxygen produced is.

2h2o2= mno2= 2h2o+ o2↑68 32

x68/32=x/

x = the mass of manganese dioxide in the mixture is.

(1) Solution: Let substance b be xgFrom the relationship between the measurement numbers of the reaction formula a+3b=2c+2d, we get 1:3=:x 11Get x=.

and from the conservation of mass to obtain the substance c. Hence b:c=:1

2) Only the mass of O2 is reduced by the question. From the metrological relationship of the reaction formula 2H2O2=2H2O+O2, O2 is, so hydrogen peroxide is. Because the mass fraction of hydrogen peroxide solution is 10%, then the water can be set to yg, which is obtained by the relation, and x= is obtained.

So the mass of manganese dioxide is.

Manganese dioxide is used as a catalyst and its mass is unchanged before and after the chemical reaction.

Using this invariant as a criterion, the change in the mass of potassium chlorate after the release of oxygen can be calculated.

Assuming that the mass of the original mixture is a gram, then potassium chlorate is a gram and manganese dioxide is a gram.

The mass of the mixture after the reaction is grams.

From this, it can be seen that the mass of oxygen produced is grams, and the mass of potassium chlorate reacted is grams (which can be obtained from the chemical reaction equation 2kclo3=2kcl+3O2).

Then the decomposition rate is very simple, *100% =

Featuring a 10g mixture with KCLO3 8g

Generate O2 2g decomposition KCLO3 decomposition rate.

(1) If there is 100L of air, O2 accounts for 21% of the air volume fraction (which should be regarded as a known constant), then it contains 21LO2Oxygen content = 21 * oxygen consumed mass = calculation has a certain format, pay attention to the unit when writing.

1. 4g

Solute mass fraction = ---100% = 20%.

4g+16g

2.NaCl mass = 16 g 20% =

Solute mass fraction = ---100% is approximately equal to.

16g+5g

Mass = 10g * 8% =

Solute mass fraction = ---100% is approximately equal to.

10g-4g

Mass = 14g 10% + 1g =

Solute mass fraction = ---100% = 16%.

14g+1g

The solute mass is 4g, and the solution mass is 4+16=20g. The mass fraction of solute 4 20*100%=20%.

The solute mass is 16 * 20% = , and the solution mass is 16 + 5 = 21g. The mass fraction of solute solute is 10*8%=, and the mass of solution is 10-4=14g. The mass fraction of solute solute is 14*10%+1=, and the mass of solution is 14+1=15g.

Mass fraction of solute.

25g*28/60=

Adults should consume at least 78 grams of protein from food per day.

Solve according to the mass invariant equation of the nitrogen element:

Solution: Let the protein mass be x, then.

x multiplied by 15% = 25g multiplied by 28 60Finally, I figured out the correct solution of x=78g!!

According to 25g of urea CO(NH2)2, the mass of N element = 25g*N%, and then divide by 15%.

The amount of carbon dioxide generated in each reaction is calculated first, m beaker + dilute hydrochloric acid + sample mass – (beaker + residue).

The amount of carbon dioxide produced can be obtained: . It is stated that even if the sample volume is increased, the maximum amount of carbon dioxide generated is that the hydrochloric acid in experiments 2 and 3 has been completely reacted, and the sodium carbonate in the sample of experiment 1 has been completely reacted, which can be used to calculate the sodium carbonate content.

The mass of sodium carbonate is calculated from the amount of carbon dioxide generated, then its mass fraction

It's very clear upstairs!