Chemistry 78 two questions, 27 questions Chemistry.

7b8c.7 entropy increases, and sulfuric acid is high boiling point and difficult to volatilize, can not cause entropy increase 8 iron hydroxide colloids are not precipitate.

7 Option A Because the hydrochloric acid produced by its hydrolysis is volatile, then the disorder increases, and the equilibrium shifts to the right, and the entropy increases.

8, A is wrong, carbon dioxide is excessive, bicarbonate should be generated, B is wrong, bicarbonate should be generated, carbonate will react with phenol to generate, phenol and bicarbonate, D wrong, colloid, you can't play the precipitation symbol, otherwise it is precipitation, not colloid, colloidal should be written in the back, choose C to set a small amount of sodium bicarbonate as 1, there is 1mol bicarbonate + 1mol hydroxide + 1mol barium ion = 1mol water + 1mol barium carbonate.

d, c, d are colloids generated, not precipitates.

Small outer flame outer flame water and carbon dioxide.

The steam of a white smoke candle (either n-octane or n-18 or 22-cane).

26.1. Extraction separating funnel beaker 2. Starch turns blue iodine 27(1) NaCl(S)+H2SO4 (concentrated) slightly hot NaHSO4+HCl;

2）b；a；f；Water is inverted and sucked into the gas collection cylinder;

3) Concentrated sulfuric acid.

The amount of oxygen substance is, oxygen atoms.

The gas element that can be absorbed by sodium hydroxide is halogen, generally chlorine, which isolates the air and has a constant mass. , chlorine atom.

The reddish-brown solid is generally iron oxide 16 160 =, so the iron atom and oxygen atom are so n (fe): n (cl): n (o) = :(: 3:12 so it is ferric perchlorate fe (clo4) 3

Electronic type of chlorine.

Are you taking the wrong answer and really don't think about it anymore?

7、b，8、b

7. If the filter residue obtained by adding zinc powder to replace iron and copper will produce gas by adding acid, it means that at least iron exists and may even have zinc, because copper will not be dissolved by dilute hydrochloric acid;

Then the replacement of iron means that the copper ions in the original solution have been completely replaced, otherwise there will be no iron in the product, because the metal active zinc is in front of the iron, the copper is behind the iron, and the zinc will first replace the copper and then replace the iron;

Then after the analysis, look at the options:

aThat's right, zinc powder will be replaced when it encounters a solution of ferrous ions and copper ions to produce zinc ions;

b indicates that there are copper ions in the solution to show blue, which is inconsistent with our analysis, and the solution contains iron ions at most and shows light green;

c That's right, you can know it from the analysis;

D That's right, the relative atomic mass of zinc 65 is greater than that of iron 56 and copper 64, and it is a one-to-one quantity displacement of a substance, as long as the displacement occurs, the mass of the metal will decrease (a mass atom is replaced by a small atom, the total number remains the same).

8. When designing an experiment to determine a certain property, the other properties of the subject must be exactly the same, which is one of the basic logics of designing the experiment;

a. The surface of the aluminum wire will have a dense alumina film because it is exposed to air, and this film will block and protect the inner layer of aluminum from reacting with the outside world, so we need to polish this film to let it be polished off to get the surface of aluminum;

b. The shape is the same, the composition is different, and one reaction is more intense than the other under the same conditions, so the activity of the reaction is stronger, mg is greater than al, and the conclusions of the experimental process are correct;

c. If you want to measure the activity of zinc and iron, then you should keep the two consistent, both are filamentous or powdery, we all know that the contact area will be conducive to the reaction speed, then a pile of zinc powder and a wire are not comparable to the experiment;

d. The experimental design is correct, the same shape is only different in composition, one can be dissolved by acid, the other has no change with acid, the activity of the metal dissolved by acid is greater, Fe is greater than Cu, but the conclusion is wrong, so the option is not correct.

There are two possibilities for bubble description: 1. Zinc happens to replace copper and iron, 2. There is an excess of zinc powder.

A conclusion is wrong c The contact area of the reactants is different, one is a powder and the other is a solid D is wrong.

7, d iodine should be extracted with carbon tetrachloride to remove ethanol can be washed with water for many times sodium chloride solubility is stable, 8, b should be filtered after reaction. Remove excess precipitate so as not to affect the experiment. Barium reacts only with carbonate, first.

Magnesium can react with carbonate and hydroxide, second. Chloride and silver ions react. Third.

Question 7 choose B, elimination method, if you add mg ions first, CO3 roots and OH roots will precipitate, so the excluded roots and Ag ions can not coexist, Ag ions and Cl ions will precipitate, so D is excluded.

The addition of Ba2+ can only separate CO32-, the addition of Mg2+ can only separate OH-, and finally the addition of AG+ can separate Cl-.

There will be gas production, BaCl2 will produce precipitation, and NaCl will not occur.

7.If the amount of the solution before dilution is mg, then there is: m*10%=(m-100)*20%.

Solution: m=200g; n(naoh)=m/m=200*10%/40=

c=n v= A: Omitted.

8.The concentration of concentrated H2SO4 is C1 = 1000 * D * W M = 1000 * According to the law of dilution: C1V1 = C2V2, then there is: C2 = 250 * 1 Brother Bend Answer: Slightly.

7、d8、b。The mass fraction of solutes is increased, excluding a; When solid potassium nitrate is added, the solute mass fraction of the solution is not 0, and c is excluded; When the solution reaches saturation, the mass fraction of the solute does not increase, and d is excluded. Only B is correct.

Question 7 is all false, i.e. choose D

cao+naoh generates salt and water so error.

Na2CO3 is alkaline so false.

H2SO4 is oxygenated but not oxide Error.

co is not organic, so wrong.

The mass fraction of the solute in option B is increased in the 8th option, and A is excluded

No solute is added, and the solute mass fraction of the solution is not 0, c is wrong;

When the solution reaches saturation, the mass fraction of the solute will not continue to increase, so D is wrong, so B is selected

7 We haven't learned yet, 8 choose b, I hope it can help you o