Junior 2 Science Questions, Masters Rush !!!!

1) The solubility of a at 40 is 40g, so the mass ratio of solvent to solute in saturated solution is 100g:40g=5:2. Remember: solubility indicates a saturated solution, implying a solvent mass of 100 g.

2) At 40, the solute mass fraction of the saturated solution is calculated with the solubility of a (that is, the maximum solute mass fraction of a solution at 40) is 40 (40+100)*100%, and 25 (25+25)*100%=50%, because 50%, so the solute mass fraction of the final solution is.

2 m = 25 * 37 100 = g.

Quality = g (g + 25g).

The answer is your own.

The answer is as follows: solubility refers to the number of grams dissolved by a substance when it reaches saturation in 100 grams of solvent at a certain temperature.

1) Look at ** to know that the solubility at 40 is 40 grams.

So there is 100 grams: 40 grams = 5:2

2) At 40, there is solvent:solute = 5:2

So 25 grams of water:a mass = 5:2

The mass of a can be obtained = 10 grams, that is, only 10 grams of a will be saturated if only 10 grams of a are dissolved, then the mass fraction = 10 grams (10 grams + 25 grams) = 2 7

The details are not :

(1) From the change relationship table, it can be seen that when there is no object on the pallet, that is, when the pressure is 0, the resistance of R1 is 300

2) In a series circuit, u=u1+u0; Since u0=u-table=2v, u1=u-u-table=3v-2v=1v

That is, the voltage on the pressure sensor R1 is 1V;

3) In a series circuit, the ratio of voltage is equal to the ratio of resistance, that is, u0 u1=r0 r1, so r1=(u1xr0) uo=(1vx100) 2v=50 The corresponding change table shows that the pressure f is 250N

Let ob be x, that is, ba is 2x, and oa is (ob+ba)=3x, which is obtained by f1xl1=f2xl2.

f pressure xoa=gxob;

g = (f pressure xoa) ob = (250nx3x) x=750n

Set xkg84 disinfectant, y liters of water, according to the topic, there is.

x+y=2000

Solve the equation to get, x=, y=

That is, disinfectant, liter of water.

1 choose D, that can only play the role of beautification of Lingwu.

2 choose B, this according to the common sense of life, such as the heat shield on the electrical appliances, etc., the bowl is made of ceramic.

2 A - 3 B ——— 1 C - Rough imitation 2

III 1 2 3 4

4. 1 1 p.m. to 1 a.m. sharp.

2 concentric circles (the guy hasn't realized that the orbit is elliptical) 3 in order to insulate the heat and prevent the heat from being lost.

b b a3 b1 c2

Wrong, right, right, right.

0 hours. Elliptical.

Thermal insulation.

While science and technology change our lives and promote social progress, they also bring many (harms) to the natural environment and human society. We must learn to think scientifically and use science and technology correctly to create a better tomorrow for mankind.

In the school laboratory, there are instruments (equipment) and reagents for students to do experiments. The storage point of the experimental instruments and reagents must meet the requirements of the respective temperature, light and ventilation of the instruments and reagents!). ）。

Emergency treatment of laboratory accidents: in case of burns or scalds, rinse with (plenty of water); If you are burned with a chemical agent, rinse with (slowly rinse with water for more than 1 minute).

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220 times 5 equals 1100w, divided by 60=, so up to 18.

2*30*18*60=64800wh=, so it consumes electricity.

1. r1 = 25 ohms.

2. V=V The measured voltage is the power supply voltage, which has nothing to do with the switch S.

Column two equations to solve on it.

Solve.

10,000,000 kilowatts = watts per hour, and the power value generated in spring is this.

The problem may be that the grill is too polluted to the air.