Which of the salts whose formulas are cas mgcl2. The most important classes of inorganic substances

Many substances that are binary compounds and do not belong to the class of salts cannot exist in solution due to complete irreversible hydrolysis.

For instance:

1. Hydrolysis of metal carbides makes it possible to obtain hydrocarbons:

2. Hydrolysis of non-metal halides leads to the formation of oxygen-containing acid and hydrogen halide:

3. Phosphides, nitrides of some metals are decomposed by water to the corresponding base and phosphine or ammonia ( hydrogen compound non-metal):

Note that in all hydrolysis reactions, the oxidation states chemical elements do not change.

Redox reactions are usually not classified as hydrolysis reactions, although in this case the substance interacts with water:

Questions and tasks to § 16

1. Select examples of organic substances undergoing hydrolysis: glucose, ethanol, bromomethane, methanal, sucrose, formic acid methyl ester, stearic acid, 2-methylbutane.

   Make equations for hydrolysis reactions; in the case of reversible hydrolysis, indicate the conditions that allow shifting the chemical equilibrium towards the formation of reaction products.

2. Which salts undergo hydrolysis? What kind of environment can have in this case aqueous solutions of salts? Give examples.
3. Which of the salts whose formulas are: Na 3 PO 4 , Cu(NO 3) 2 , K 2 SO 4 , NH 4 NO 3 , NiSO 3 , K 2 CO 3 , undergo cation hydrolysis?
4. Which of the salts, the formulas of which are: CaS, MgCl 2, Na 2 SO 3, Al 2 (S0 4) 3, HCOOK, BaI 2, Ca(NO 3) 2, undergo anion hydrolysis?

   Make equations for their hydrolysis, indicate the medium.

5. What color will the solution of each salt turn into when litmus is added: SrCl 2, Rb 2 SiO 3, BaBr 2, Fe (NO 3) 2, AlBr 3, Li 2 CO 3, Nal, KNO 3?

   Give an explanation using the hydrolysis reaction equations.

6. Will the color of solutions of the following salts change after the addition of phenolphthalein: KI, AlCl 3, K 2 SO 3, (NH 4) 2 SO 4, NaCN?

   Write the equations for hydrolysis reactions.

7. A piece of zinc was placed in a solution of zinc chloride, gas bubbles appeared. What is this gas? Explain the processes that take place in a solution.
8. Which of the following salts undergo hydrolysis both in terms of the cation and the anion: A1Br 3, FeCl 2, CoSO 4, (NH 4) 2 S0 3, KNO 2?

   Compose ionic equations their hydrolysis.

9. To 50 g of a solution of sodium carbonate with a mass fraction of a solute of 10.6%, an excess of a solution of aluminum sulfate was added. What gas was released in this case? What is its volume (n.a.)?

   Answer: 1.12 liters.

10. Place the salts in ascending order of the acidity of their aqueous solutions: NH 4 Cl, NaNO 3, Na (CH 2 ClCOO), Na (CH 3 COO), Na 2 CO 3. Give an explanation.
11. Adding which of the following substances to a solution of iron (III) chloride will enhance the hydrolysis of the salt: Hcl, NaOH, ZnCl 2, H 2 O, Zn? Give an explanation.
12. Suggest ways to suppress hydrolysis aqueous solution potassium sulfide.

DEFINITION

calcium sulfide – medium salt, formed strong base- calcium hydroxide (Ca (OH) 2) and a weak acid - hydrogen sulfide (H 2 S). The formula is CaS.

Molar mass - 72g / mol. Is a powder white color which absorbs moisture well.

Hydrolysis of calcium sulfide

Hydrolyzed at the anion. The nature of the medium is alkaline. Theoretically, a second step is possible. The hydrolysis equation looks like this:

First stage:

CaS ↔ Ca 2+ + S 2- (salt dissociation);

S 2- + HOH ↔ HS - + OH - (anion hydrolysis);

Ca 2+ + S 2- + HOH ↔ HS - + Ca 2+ + OH - (equation in ionic form);

2CaS + 2H 2 O ↔ Ca(HS) 2 + Ca(OH) 2 ↓ (molecular equation).

Second step:

Ca (HS) 2 ↔ Ca 2+ + 2HS - (salt dissociation);

HS - + HOH ↔H 2 S + OH - (anion hydrolysis);

Ca 2+ + 2HS - + HOH ↔ H 2 S + Ca 2+ + OH - (equation in ionic form);

Ca(HS) 2 + 2H 2 O ↔ 2H 2 S + Ca(OH) 2 ↓ (molecular equation).

Examples of problem solving

EXAMPLE 1

EXAMPLE 2