Chemistry solution for junior high school, chemistry for junior high school. Solution.

Why it has to be"A certain amount of solvent"At a certain temperature, it dissolves to the point that it is insoluble, and it is a saturated solution. You're right. Emphasis"A certain amount of solvent"First, according to the actual situation, our saturated solution is always configured in a certain amount of solvent, and second, the saturated solution also has a concept of saturation, which needs to be emphasized in "a certain amount of solvent".

Because the mass of the substance dissolved at different temperatures is different, for example, when dissolving sucrose in cold water to the point that it cannot be dissolved, it can continue to dissolve when it is warmed, so a certain temperature should be specified.

If you dissolve sucrose in a glass of water until it cannot be dissolved, then add water to it, it can continue to dissolve, so a certain amount of solvent should be prescribed.

I'm also a junior high school student, and chemistry is okay.

Don't blame me for my bad come!

Only under the condition of a certain temperature and a certain solvent is determined, the solute dissolved in the saturated solution is certain!

The solubility of a substance is related to temperature!

What does it mean to dissolve to the point that it is insoluble, is it not a saturated solution?

At a certain temperature, it dissolves to the point that it cannot be dissolved, and it is a saturated solution of this substance.

But this is not necessarily the case when the temperature changes, and if the temperature is not stated, there is no limit to the amount of solute in the saturated solution of a substance!! Poor expression. Haihan.

Not necessarily, you don't have a certain amount. Its saturation is different, like a gas, it is determined by the amount of pressure.

As the temperature changes, the solubility of the substance changes, and the amount of solute changes as the solvent is added. At a certain temperature, in a certain solvent, it is given a limited Kuang.

What are the ways to prepare 100g of 10% sodium carbonate solution? How many grams of each substance are needed? (Available reagents: water, sodium carbonate solids, 25% sodium carbonate solution, 5% sodium carbonate solution).

Methods Water g sodium carbonate solid g 25% sodium carbonate solution g 5% sodium carbonate solution g

1.Water 90g sodium carbonate solid 10g 25% sodium carbonate solution 0g 5% sodium carbonate solution 0g

2.Water 60g sodium carbonate solid 0g 25% sodium carbonate solution 40g 5% sodium carbonate solution 0g

3.Water g sodium carbonate solid g 25% sodium carbonate solution 25g 5% sodium carbonate solution 75g

4.Water 75g sodium carbonate solid 5g 25% sodium carbonate solution 20g 5% sodium carbonate solution 0g

5.Water: Sodium carbonate solid, 25% sodium carbonate solution, 10g, 5% sodium carbonate solution, 0g

Methods Water g sodium carbonate solid g 25% sodium carbonate solution g 5% sodium carbonate solution g

From 1 to know that there is no copper chloride, there must be barium nitrate, there may be sodium carbonate and sodium sulfate, which produces a white precipitate to produce barium sulfate or barium carbonate, and the solution containing copper ions is light blue; It is known from 2 that there must be sodium carbonate and sodium sulfate, dilute nitric acid reacts with barium carbonate to produce carbon dioxide, and barium sulfate is insoluble in dilute nitric acid. So choose B and C

c. Explanation: Barium ions react with carbonate ions and sulfate ions to form precipitates, add a sufficient amount of dilute nitric acid, and generate colorless gas carbon dioxide, which proves that there are carbonate ions; There are no copper ions, because copper ions have color, and the experiment results in a colorless solution; Potassium chloride is not sure if there is any.

Choose B, C

The white precipitate is the reaction of sodium carbonate, sodium sulfate and barium nitrate to form barium carbonate and barium sulfate, and the reaction of barium carbonate with nitric acid will dissolve the precipitate to produce carbon dioxide gas. And the solution has no color, which proves that there is no copper chloride, because copper chloride has color when dissolved in water. Potassium chloride is not sure if there is any.

a Let m be 10

A solution of 10g10 contains 1g of solute and 9g of solvent, and evaporates half of the mass (2 m), (the mass of solute does not change), that is, 1g of solute and 10 2-1=4g of solvent.

That's 20 percent

a. The mass of the evaporated solvent is half the mass of the solution, i.e. mg2

b Same as AC plus solute mass of mg8 (x=mg8

d m*10%+y*40%=(m+y)*20% y=mg/2

c Because solute + solvent = solution.

If the solvent does not change, the concentration of the solution increases.

d: The solubility of calcium hydroxide in lime water decreases with increasing temperature! Whereas quicklime dissolves in water and is exothermic.

: D, 3 and 4 are correct.

Because, after adding a small amount of white anhydrous copper sulfate powder, the water in the original saturated solution of copper sulfate is combined with anhydrous copper sulfate powder to form copper sulfate crystals, so that the solvent water in the saturated solution is reduced, resulting in a reduction in the soluble solute, so 3 and 4 are correct.

d Anhydrous copper sulfate powder is combined with water to become copper sulfate, and the copper sulfate crystals are precipitated when the water is less