1. Which statement is incorrect? 1) The volumetric fraction of oxygen in the air is 21%. 2) Mountain air is a pure

1. Which statement is incorrect?
1) The volumetric fraction of oxygen in the air is 21%.
2) Mountain air is a pure substance.
3) Air contains 0.03% carbon dioxide.
4) Air is a mixture of oxygen, nitrogen, carbon dioxide, and inert gases.

2. Hydrogen, like oxygen, is not found in the Earth’s crust; it forms allotropes, is present in all oxides, and forms diatomic molecules.

3. The oxide with the «extra» formula is:
Cu2O;
FeO;
K2O;
NO.

4. The lowest mass fraction of oxygen in an oxide with the formula:
1) Na2O;
2) Li2O;
3) Cu2O;
4) H2O.

5. Both substances with the formulas are bases:
1) Ca(OH)2, KNO3;
2) KOH, Cu(OH)2;
3) Ba(OH)2, NaOH;
4) HCl, Na2O.

6. Select the acid formula whose salts are called nitrates.
1) HNO3;
2) H3N;
3) NaNO3;
4) HNO2.

7. The amount of nitrogen substance with a mass of 140 g and the volume it occupies are respectively equal to:
10 moles, 1.12 liters;
5 moles, 112 liters;
5 moles, 22.4 liters;
10 moles, 224 liters.

8. The mass of the salt obtained by evaporating 300 g of its solution with a mass fraction of 15% is:
15 g;
30 g;
20 g;
45 g.

9. The mass of sodium hydroxide (g) in 80 ml of a 25% solution with a density of 1.28 g/ml is:
1) 19.5 g;
2) 20.3 g;
3) 25.6 g;
4) 26.7 g.

10. Are the statements correct?
A. Water dissolves only liquid and solid substances.
B. When substances dissolve, heat may be released or absorbed.
1) Only A is correct;
2) Only B is correct;
3) Both statements are correct;
4) Both statements are incorrect.

PART 2. Multiple-choice test with two correct answers.

11. The following statements are correct:
Hydrogen and oxygen can be collected by displacing water from a container;
Oxygen is produced in industry by the decomposition of hydrogen peroxide;
Hydrogen is detected by a glowing splint;
Oxygen is recognized by the clouding of limewater;
Hydrogen is produced by the reaction of an acid with a metal.

Matching test.

12. Establish a correspondence between the class of substance and the formula of that substance.
REACTION EQUATION
A) Acids;
REACTION TYPE
1) MgSO4;
B) Bases;
2) Li2O;
C) Salts.
3) H2SO3;
4) KOH;
5) CO2.

Open-ended questions.

13. A sample of carbon was burned in oxygen. The product of the reaction was dissolved in water, and the resulting solution turned methyl orange red. Write the corresponding reaction equations.

14. Ammonia NH3 is a raw material for the production of fertilizers, nitric acid, explosives, and synthetic fibers, obtained by the reaction of nitrogen and hydrogen. Determine the volume of ammonia that can be obtained from 5 moles of nitrogen.