1 middle school chemistry question, 1 middle school chemistry question

The easiest way is to find pH test strips, NaCl is neutral, NaCO3 is alkaline.

It is also possible to use acid-base indicators, and it is NACO3 that is blued with litmus.

It is also possible to add agno3, and it is NaCl that produces the precipitate and CaCl2 is Na2CO3 that produces the precipitate

The addition of HCl produces a gas that is Na2CO3

In conclusion, there are many methods of identification.

The addition of hydrochloric acid produces sodium carbonate with bubbles.

There are no bubbles in the sodium chloride.

It is most convenient to test directly with pH test strip, because Na2CO3 is hydrolyzed and alkaline, while NaCl is neutral.

Don't taste it directly, because the most basic principle in a chemistry lab is not to taste the medicine directly.

You can also use CaCl2, HCl, but not Agno3, because both AgCl and Ag2CO3 are white precipitates.

Add silver nitrate, then add dilute nitric acid, and the white insoluble solid is sodium chloride.

Dilute hydrochloric acid can also be added, and sodium carbonate is produced by bubbles.

Or add a certain amount of water, add phenolphthalein, and turn red into sodium carbonate.

There are a lot of ways)

After the addition of Ca(NO3)2, there is Na2CO3 with precipitation, and NaCl without precipitation.

Add acid. Na2CO3 is formed by bubbles, and NaCl is not obvious.

The gas produced is CO2.

1. Taste, NaCl salty, Na2CO3 bitter.

2. Take part of the dissolution, Na2CO3 is alkaline, which can make litmus blue, and NaCl solution can not make litmus discolor.

3. Take a part of the dissolution, drop dilute hydrochloric acid, bubbling is Na2CO34, take a part of the dissolution, drop clear lime water, and have a precipitate of Na2CO3

Memorize the standard writing of acids and bases.

This is to look at the reaction between the metal and the acid or sodium hydroxide.

They differ in their solubility in water, but the addition of protosolutes can make them both saturated solutions.

b Lime water, I remember that the lower the temperature, the greater the solubility, and the saturated solution is generally heated to evaporate water.

After the mass reaction of D and E is measured experimentally, the sum is increased respectively, that is, the water is, and the CO2 is C:H=1:5, so from the alternative answer, it can be seen that H2 and CH4 coexist in this gas.

You omit the most critical thing of the question, and only after checking it will you know the original question.

The use of A and the turbidity must contain CO2, and C also indicates that there is CO in the reaction.

Therefore, C should be chosen.

d is wrong, the element cannot be said to contain, it can only be said to be composed of what element, for example, magnesium-rich silicate is composed of hydrogen, magnesium, silicon, and oxygen.

If the question is correct, the answer is wrong, and the Anshan Jade Buddha in A is obviously a mixture, and the magnesium-rich silicate is pure.

d should be correct.

Magnesium-rich silicate is a pure substance that is a microscopic substance, which can only be said to be composed of these elements, or a magnesium-rich silicate molecule contains several certain atoms, and cannot be said to contain elements.

The solute mass is: 100*10% +=

The mass of the solution is: 100+ =

The resulting solute mass fraction in solution is =

The solute mass fraction in the resulting solution = (100g 10%+ (100g + 100%)=20%.

According to the law of conservation of mass, only iron powder reacts, producing hydrogen.

According to the equation, it is concluded that iron powder has, ferrous chloride.

So copper powder has.

So the quality of the solution.

The solute mass fraction is.