What is the idea of these two questions?

Question 7: a, false. Because the temperature determines the kw. The pH of the neutral solution is different at different temperatures. pH=6 at 90 is neutral.

b. False. Because the alkalinity of ammonia must be reduced when diluted, this means that the concentration of H+ increases.

c, correct. Because acetic acid is a weak acid. If you replace the acetic acid in the question with a strong acid, the pH will be 7 after mixing. But acetic acid still ionizes a part of it after it is consumed, so the acid is excessive.

D: False. The mixed solute can be regarded as mainly composed of KhCO3, K2SO4, and KCl. Obviously, the solution should be alkaline.

Question 10: a, correct. The concentration of all particles containing a atom before mixing is. After mixing, it becomes. Whereas, the particles containing a atom are only ha and a-.

c, correct. Conservation of charge.

b, correct. As can be seen from the title, the concentration of hydrogen ions is greater than that of hydroxide ions, and the concentration of sodium ions is greater than that of chloride ions. In order to maintain the conservation of charge, the concentration of a ion must be greater than HA.

D: False. Inference from option a, c(na+) = c(a-) + c(ha).

If there is anything I don't understand or I have made a mistake, ask again

The words of a are related to temperature, and the words b are wrong, and c adds up to 14 who is stronger.

10.It really doesn't work, and it is assumed that A is nitrate.

The interval in the question should be: (,1), and the argument is as follows:

There are two types of people who like to learn Chinese, one is those who only like to learn Chinese, which is marked as A, and the other is those who like to learn Chinese and like to learn mathematics at the same time (this kind of person is what they want), which is recorded as C.

In the same way, there are two types of people who like to learn mathematics, one is only like to learn mathematics, which is marked as A, and the other is those who like to learn mathematics and like to learn Chinese at the same time (this kind of person is what they want, and the same group of people as above) is C.

And 35+43 is a+b+c+c, where a+b+c is the 46 students in the class, so c=35+43-(a+b+c)=35+43-46=32 (people)If you don't understand this, I can't help you.

B, 16n should be chosen.

Movable pulleys can save half the effort.

The reading of the spring is equal to the force f, i.e., f = 8n

So the frictional resistance is equal to 2 times the tensile force f, 2 8 = 16n.

The pulley is a movable pulley, and the size of the tensile force f is the same as that of the spring dynamometer, because the object moves at a uniform speed, so the force received by the object is the balance force, and the magnitude of the friction force can be calculated by using the balance of the force.

For this type you must remember to multiply f by 2

Think of it this way, what you have read is 2 7 of the whole book, plus 90 pages, and what you have read 2 5 is 2 7 2 5 = 4 35 of the whole book, plus 90 2 5 = 36 pages.

The known fraction is 2 7 + 4 35 = 14 35 = 2 5, the known number of pages is 90 + 36 = 126, and the score corresponding to 126 pages is 1-2 5 = 3 5

All pages = 126 3 5 = 126 5 3 = 42 5 = 210 pages.

The book has n pages.

List the equations according to the problem.

n-((2 7)n+90)=(2 5) (2 7)n+90) solves n=210

So there are 210 pages in total.

Solution: Ministry Department * 111111 Department * 3 * 7 * 11 * 13 * 37 So: Er = 3, or Er = 7

Multiply a digit by 3 or 7, and its mantissa is still its own number, which can only be 5, so: part = 5

Ministry, Min

When = 3, 555555 3 = 185185 (not in place, discard) When = 7, 555555 7 = 79365

Therefore: children represent 7, children represent 9, clubs represent 3, music represents 6, and the ministry represents 5 children + children + clubs + music + departments = 7 + 9 + 3 + 6 + 5 = 30

79365*7＝555555

According to the topic: Ministry, Ministry, 111111 Ministry, The number that can be multiplied by 3 or 7 while the mantissa is equal to itself is only 5. Therefore, the part 5 and the original multiplier 5th place is the child, after multiplication, it can be carried and the 6th place of the product is 5 is only 7, so the child is 7

After Part 5 and Child 7 are determined, it is not difficult to derive.

Add 6 or add 6 to make a perfect flat. Add 6x to be (3 + 1) squared, plus 6 to be (3 1) squared.

Select b, when 0 degrees is displayed, the display is 10 degrees, the boiling water at standard atmospheric pressure is 100 degrees, and the display is 90 degrees, which proves that this scale is on the scale of 10 degrees -90 degrees, and the temperature span is 100 degrees Celsius, by the formula, 80 scales 100 = the required scale 60, and the required scale is 48 + the base 10 degrees is equal to 58 degrees.

100 degrees is equivalent to 90-10=80 degrees.

1 degree is equivalent to 80 100 = degrees.

60 degrees = 10+ degrees.

1.Judging by the crystal type, choose (c).

Alcl molecular crystals.

HCl molecular crystals.

MgCl ionic crystals.

SiCl molecular crystals.