A junior high school science topic... Urgent

First of all, let me give you an analysis, Na2CO3 + NaCl mixture reacts with hydrochloric acid, in fact, only Na2CO3 reacts with hydrochloric acid; After the addition of NaOH, it happens to be completely reacting, indicating that there is still excess hydrochloric acid in the previous reaction.

HCl + NaOH = NaCl + H2O molecular mass) 40x10%.

M1 40 is clear that M1 = M1 indicates the amount of hydrochloric acid that reacts with NaOH off.

The second problem is actually to find that the Na2CO3+NaCl mixture reacts with hydrochloric acid to produce gas, and the gas is volatile.

na2co3 + 2hcl = 2nacl + h2o + co244

m2 brings m1 in, giving m2=

then i.e. the quality of the final solution).

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Do the math yourself, don't cultivate your own inertia, no one will give you auspicious answers, in fact, you can read more reference books.

1 All (1) acid ions.

2) Sodium ion sulfate ion.

3) Establishment.

1) Because only Cl- and SO4 2- are different from HCL HCL and H2SO4 sulfuric acid (2)1 In the reaction, Na2SO4 is added to hydrochloric acid without obvious change, that is, Na+ and SO4 2- are added without obvious change, so Na+ and SO4 2- have an effect on the reactants.

3) Because it is known that Na+ and SO4 2- have no effect on the rate of reaction between H+ and Al, and NaCl is added to sulfuric acid in the 2 test, that is, there are Cl-, SO4 2- and Na+ in the solution, so Cl- can promote the reaction of aluminum and acid.

So the conjecture holds.

(1) When the battery is discharged, chemical.

Chemical energy is converted into electrical energy

2) If the mass of lead in a battery is 1800 grams, and the 36% dilute sulfuric acid is 1200 grams, when there are grams of lead to participate in the reaction, how many grams of solute in dilute sulfuric acid need to be consumed? What is the mass fraction of the solute of the sulfuric acid solution in the battery at this time? (The final result is kept to two decimal places) Test Center:

calculations based on chemical reaction equations; Simple calculations of solute mass fractions; Energy changes when a substance undergoes a chemical change Special topic: Composition of solutions and calculation of solute mass fraction; Calculation of chemical equations Analysis: (1) The discharge of the battery is the result of chemical change PBO2 (solid) + 2H2SO4 + PB = 2PBSO4 + 2H2O, therefore, the discharge is the conversion of chemical energy into electrical energy;

2) According to the chemical equation of the reaction, the mass of the consumed sulfuric acid and the mass of the generated water are calculated by the mass of the lead participating in the reaction, the difference between the quality of the sulfuric acid in the original sulfuric acid solution and the quality of the consumed sulfuric acid is the mass of the remaining sulfuric acid in the solution after the reaction, and then the mass fraction of the sulfuric acid solution in the battery after the reaction is calculated by using the solution composed of the remaining dilute sulfuric acid and the generated water, and the mass fraction of the solute in the battery is calculated by using the solute mass fraction calculation formula Answer: Solution: (1) The electrical energy during discharge is generated by the reaction of PBO2 (solid) + 2H2SO4 + PB=2PBSO4 + 2H2O, so this process is the process of converting chemical energy into electrical energy;

So the answer is: chemistry;

2) Let the mass of pure dilute sulfuric acid to be consumed be x, and the mass of the water to be generated is y

PBO2 (solid) + 2H2SO4 + PB = 2PBSO4 + 2H2O

x y196 x =207 x=294g

207 =36 y y=54g

36% dilute sulfuric acid 1200 g of dilute sulfuric acid in the mass of sulfuric acid = 1200g 36% = 432g, then the mass of sulfuric acid remaining after the reaction = 432g-294g = 138g

The mass of the remaining sulfuric acid solution = 1200g-294g + 54g = 960g

Mass fraction of solute in sulfuric acid solution = 138g 960g 100% =

Answer: The solute in the dilute sulfuric acid needs to be consumed is 294 grams, and the mass fraction of the solute in the sulfuric acid solution in the battery is.

Other methods of understanding are also given points) Comments: When answering this question, it should be noted that the reaction only produces lead sulfate precipitate and water, so the solution obtained after the reaction is completed is the quality of the remaining dilute sulfuric acid and the quality of the water generated

(1) Chemical energy (2) consumes 294g, mass fraction (1200*36%-294) 1200-294g solute + 54gh2o=

Answer: 1. Adding an appropriate amount of water dilution has no effect on the experimental results. (Because titration with sodium hydroxide is an acid-base neutralization, the amount of sodium hydroxide will not be reduced as long as the amount of acetic acid is not reduced.) ）

2.First, add a small amount of phenolphthalein to the white vinegar, and then add sodium hydroxide solution dropwise to the white vinegar until the solution turns red.

3.Not true. The calculation is:

Because they are 1:1 reactions. So to calculate the number of moles of acetic acid should be:

The volume of white vinegar multiplied by the density divided by the relative molecular mass of acetic acid (60g mol), the number of moles of sodium hydroxide is calculated: volume multiplied by density multiplied by the mass fraction of the solution divided by the molar mass of sodium hydroxide. Finally, use two moles to compare.

an=0&si=4 Here the question, I have a question, why the area of the second question s pqr is calculated to be s more than a group. Nothing is known. Bird poop may be offset when calculating the area! Take a closer look.

A is elemental copper.

b is copper oxide.

c is copper sulphate.