###### Periodic Table

Changing the properties of oxides from basic to acidic takes place in the ranks:

Changing the properties of oxides from basic to acidic takes place in the ranks: $$Li_2O → BeO → B_2O_3$$$$MgO → Al_2O_3 → SiO_2$$.

###### Periodic Table

A number of chemical elements, such as silicon, aluminum, magnesium, sodium are characterized by the following regularities:

A number of chemical elements, such as silicon, aluminum, magnesium, sodium are characterized by decreasing of the relative atomic mass.

###### Periodic Table

Three electrons are in the outer electronic layer of  each of the two atoms of chemical elements:

Three electrons are in the outer electronic layer of each of the two atoms of chemical elements: Al and B

###### Periodic Table

In which series the oxidizing properties of atoms decreases?

The oxidizing properties of atoms decreases in the series $$Cl → Br → I$$

###### Group I of the Periodic Table

The chemical element, located in the 3rd period, the IA-group corresponds to a diagram of the electronic structure of the atom

The chemical element, in the 3rd period, the IA-group corresponds to a diagram of the electronic structure of the atom 2; 8; 1

###### Group I of the Periodic Table

In equation chemical reaction scheme wherein $$Na + H_2O → NaOH + H_2$$, the sum of all the coefficients is…

In equation chemical reaction scheme wherein $$Na + H_2O → NaOH + H_2$$, the sum of all the coefficients is 8.

$$2Na + 2H_2O → 2NaOH + H_2$$

###### Group I of the Periodic Table

In  the electrolytic dissociation of which substance metal cations and hydroxide ions in a solution are formed?

Metal cations and hydroxide ions are produced in a solution in the electrolytic dissociation of lithium hydroxide: $$LiOH \to Li^{2+} + OH^-$$

###### Group I of the Periodic Table

Among the chemical elements  $$K → Na → Li$$

Among the chemical elements  $$K → Na → Li$$ weaker reducing properties.

###### Group VII of the Periodic Table

Which chlorine compounds have the highest and the lowest number of oxidation, respectively

The highest number of oxidation (+7): $$Cl_2O_7$$

The lowest number of oxidation (_1): $$NH_4Cl$$

###### Group VII of the Periodic Table

Model of which atom is shown in the figure?

The illustration shows the fluorine atom.

###### Group VII of the Periodic Table

. A number of chemical elements fluorine, chlorine, bromine, iodine, are characterized by the following changes in regularities characteristics:

A number of chemical elements fluorine, chlorine, bromine, iodine, are characterized by the following changes in regularities characteristics: increase in the number of electronic layers; decrease in oxidative ability.

###### Group VII of the Periodic Table

How many protons are there in the nucleus of an atom of a chemical element, which is located in the 2nd period, VIIA group? electronic layers; decrease in oxidative ability.

There are 9 protons in the nucleus of an atom of a chemical element, which is located in the 2nd period, VIIA group. This is fluorine. It has 9 electrons. The number of electrons corresponds to the number of protons.

###### Oxygen and oxides

In which compound of oxygen has oxidation number -1?

The oxidation number -1 is in the compound $$Na_2O_2$$ oxygen exhibits.

###### Oxygen and oxides

True or not the following propositions about chemical pollution and its consequences?

А. Elevated levels of indoor carbon (II) oxide is dangerous for human health.

B. Emissions of gaseous industrial waste of sulfuric and nitric acids adversely affect human health.

Both propositions are true

###### Oxygen and oxides

With which of these compounds oxygen reacts under normal conditions?

Oxygen reacts with sodium under normal conditions.

###### Oxygen and oxides

The number of electrons in the outer electronic layer of an atom with a nuclear charge + 16 is equal to ...

The number of electrons in the outer electronic layer of an atom with a nuclear charge + 16 is equal to 8.

###### Hydrogen and water

Mass of 5.4 g of aluminum may react with 219 g of hydrochloric acid solution. Determine the percent concentration of the acid in the solution.

The reaction is $$Al + 6HCl \to 2AlCl_3 + 3H_2$$

The amount of substance of Al: $$n(Al) = m(Al)/M_r(Al) = 5,4/27 = 0,2 mo$$l

The amount of substance of HCl: $$n(HCl) = 6*n(Al) = 6*0,2 = 1,2 mol$$

The mass of HCl: $$m(HCl) = n(HCl) * M_r(HCl) = 1,2*36,5 = 43,8$$

Persentage of HCl:$$\omega = (m(HCl)/m_{sol})*100 = 43,8/219 = 20$$

###### Hydrogen and water

The reaction involving water included in each of the two compounds:

The reaction involving water included in each of the two compounds: $$SO_3$$ and $$BaO$$

$$SO_3 + H_2O \to H_2SO_4$$

$$BaO + H_2O \to Ba(OH)_2$$

###### Hydrogen and water

What substances will react with hydrogen?

Each of two substances $$CuO, S$$ reacts with hydrogen.

$$CuO + H_2 \to Cu + H_2O$$

$$S + H_2 \to H_2S$$

###### Hydrogen and water

In equation chemical reaction scheme wherein $$Fe_2O_3 + H_2 → Fe + H_2O$$, the sum of all the coefficients is…

In equation chemical reaction scheme wherein $$Fe_2O_3 + H_2 → Fe + H_2O$$, the sum of all the coefficients is 9

$$Fe_2O_3 + 3H_2 → 2Fe + 3H_2O$$

###### Reactivity series

Which substances interact will calcium?

Calcium interacts with chlorine and hydrochloric acid.

###### Reactivity series

Between what substances can be a chemical reaction?

This reaction is $$2NaOH + CaO \to Ca(OH)_2 + Na_2O$$

###### Reactivity series

What substance can be used for dissolution of iron hydroxide (II) solution?

For the dissolution of iron hydroxide (II) solution can be used sulfuric acid

###### Reactivity series

Sulfuric acid solution reacts with each of two substances:

Sulfuric acid solution reacts with each of the two substances: $$Zn, Zn(OH)_2$$

###### Tests for ions and gases

Irreversible ion exchange of the reaction between barium hydroxide and potassium carbonate solution due to the interaction of the ions…

Irreversible ion exchange of the reaction between barium hydroxide and potassium carbonate solution due to the interaction of the ions $$Ba^{2+}$$ and $$CO_2^{−3}$$

###### Tests for ions and gases

In which reaction gas evolution does not occur?

The gas is not released during the reaction of aqueous solutions $$Na_2CO_3 + Ba(OH)_2$$

###### Tests for ions and gases

In which case, a precipitate is formed?

The precipitate is formed by reacting aqueous solutions $$AgNO_3 + KBr$$

###### Tests for ions and gases

Indication of the chemical reaction between hydrogen and copper oxide is…

Indication of the chemical reaction between hydrogen and copper oxide is precipitation.

$$CuO + H_2 \to Cu + H_2O$$