A chemistry question, alkali metals, what are the common strong bases in chemistry, such as many sub

Let the alkali metal be m, the molar mass be r, the metal mass be x, and the oxide be y2m+2h2o=2moh+h2 weight gain.

2r...34

x...17x/r

m2o+h2o=2moh weight gain.

2r+16...18

y...9y/(r+8)

So there is x+y=,17x r+9y (r+8)=m=7 into x=,y=, rounded off.

Substitute m=23 to get x=, y=, rounded off.

Substituting m=39 into x=, y=

So the oxide is K2O and the amount of the substance is.

First of all, we don't know what kind of metal it is, let's set it to na

2na+2h2o=2naoh+h2x y

na2o+h2o=2naoh

Solving a binary equation yields results.

If there is no solution, it can be replaced by k or li, because there is no indication of what kind of metal it is, so that's all.

Upstairs is right.

This is actually a kind of problem, you first know the nature of the reaction, the increase in mass is the reaction of alkali metals and water, and then write the chemical reaction equation, and then do it according to the proportional relationship corresponding to the coefficient. (The reaction of alkali metals with water can be seen as the reaction of NA and water, they are both the same).

Alkali metal name: lithium or sodium, potassium, rubidium, cesium.

Alkali Metal Element Symbol LI NA K RB CS** Chemical Formula of Oxide Li2O Na2O K2O RB2O CS2O Oxide Chemistry Zen Dry Formula of Hexun Cave Hydrogenic Compound Lioh Naoh K Oh RBOHH CSOH

Usually refers to a bitter substance whose solution can discolor a specific indicator (e.g., turning litmus blue, phenolphthalein red, etc.), and in the standard case, the pH value is greater than 7The ions ionized in the aqueous solution are all hydroxide ions, which react with acids to form salts and water. The so-called strong base and weak base are relatively speaking,-- alkali can be completely ionized when dissolved in water, and they belong to strong bases.

For example: caustic soda [sodium hydroxide, Naoh], hydrated lime [calcium hydroxide, Ca(OH)2], barium hydroxide [Ba(OH)2], potassium hydroxide [KOH], cesium hydroxide [CSOH], - active metals correspond to alkalis that are generally strong alkalis.

A broader concept of a base refers to a substance that donates electrons, or a substance that accepts protons.

The alkalinity is derived from the acid-base proton theory, and the strong alkali is the one with a strong ability to accept protons.

Strong alkalis are divided into organic strong bases and inorganic strong bases.

Among the inorganic strong bases, amino compounds (such as potassium amino, sodium amino, etc.) and alkali metal hydrides (Nah, Kh, etc.) are the most alkaline, and then the above hydroxides.

Among the strong organic bases, organometallides are the most alkaline, such as organometallic lithium compounds (such as butyllithium, diisopropyl lithium ammonia, benzyl lithium, etc.), Grignard reagent, alkyl copper lithium, etc. Then there is sodium or potassium alk (such as sodium methoxide, sodium ethoxide, potassium ethanol, sodium tert-butanol, etc.).The above organic strong alkali alkalinity is stronger than sodium hydroxide.

Guanidine and quaternary ammonium are also strong organic bases, and their alkalinity is comparable to sodium hydroxide.

Solution: a The density of lithium is less than that of kerosene;

The density of b Li, Na and K is less than that of water, and the density of RB and Cs is greater than that of water.

c Lithium reacts with oxygen to produce only lithium oxide;

d Judged by the physical properties of alkali metals

a The density of lithium is less than that of kerosene, floating on the surface of kerosene, can not isolate the air, should be stored in paraffin, so a is wrong;

b rb and cs are denser than water and sink to the bottom of the water, so b is wrong;

c lithium reacts with oxygen to produce only lithium oxide, so c is wrong;

d The hardness of alkali metals is relatively small, the density is relatively small, and the melting point is relatively low, so d is correct;

Therefore, d 4, in the following statements about alkali metals, it is correct that ( ) a alkali metals can be preserved in kerosene.

b Alkali metals react with water and float on the surface of the water.

c Alkali metals can form a variety of oxides when heated in air.

d Alkali metals have low hardness, low density and low melting point.

The alkaline gold radical brother is envious

2r+2h2o=2roh+h2

r:h2=2:1

Molecular weight 39, potassium k

Analysis: 2Na + 2H2O == 2NaOH + H2 46 2

m(na) solves: m(na) =

m(Na2O) = (

The sodium oxidized is 46 62 =

Option A Idea Analysis: Analyze the information according to the question and consider it according to the chemical reaction equation.

The unoxidized NA mass is calculated with hydrogen, and then the total mass is subtracted.

2na+2h2o===2naoh+h2

The corresponding oxidized mass is.

2na~h2

The rest is Na2O

where the mass of the Na element is A

This is actually simple, whether Na is oxidized to Na2O2 or Na2O does not produce hydrogen with water, so hydrogen is all obtained by Na reaction, and the ratio of Na to hydrogen is 1: so H2 Na is that is, then the rest is to choose A