Equations

Equations P and Q represent two reactions which describe methods of preparing \(CO_2\)

\(P) CH_4+2O_2 \)\(CO_2+2H_2O\)

\(Q) CaCO_3\)\(CaO+CO_2\)

Answer 2 (P – combustion; Q – decomposition). Combustion reaction: the products of this reaction are always carbon dioxide and water. Decomposition reaction: any compound breaks into parts.

Formulae

The formulae of compounds W, X and Y are shown. These are ions with a positive charge.
 

W \(FeSO_4*7H_2O\)

X \(Na_2CO_3*10H_2O\)

Y \(BeC_2O_4*H_2O\)

 

Which statement is correct?

W contains 14 atoms of hydrogen and 11 atoms of oxygen;

X contains 20 atoms of hydrogen and 13 atoms of oxygen;

Y contains 2 atoms of hydrogen and 5 atoms of oxygen.

Reactions

Chemical reaction with the release of heat is called:

The reaction is exothermic.

Equations

In the scheme of  transformations:  \(SiO_2 (+ X) \to K_2SiO_3 (+ Y) \to BaSiO_3\), X and Y substances are, respectively

The correct answer is 3 (\(KOH\)\(BaCl_2\))

\(SiO_2 + 2KOH \to K_2SIO_3 + H_2O\)

\(K_2SIO_3 + BaCl_2 \to BaSiO_3 + 2KCl\)

Equations

In the scheme of  transformations:  \(Al_2(SO_4)_3 \to X_1 \to X_2 \to AlCl_3, X_1 and X_2 \) substances are, respectively

The correct answer is 4 (\(Al(OH)_3, A_2O_3\)).

\(Al_2(SO_4)_3 + 6NaOH \to 2Al(OH)_3 + 3Na_2SO_4\)

\(2Al(OH)_3 \to Al_2O_3 + 3H_2O\)

\(Al_2O_3 + 6HCl \to 2AlCl_3 + 3H_2O\)

Equations

Which reactions are the reactions of ion exchange?

This reaction is \(KOH + HCl \to KCl + H_2O\)

Amount of substance

The greatest amount of sodium ions is formed by dissociation of 1 mole solution of

3 mole of sodium ions are formed by dissociation of 1 mole of sodium phosphate.

\(Na_3PO_4 \leftrightarrow 3Na^+ + PO_4^{3-}\)

 

Amount of substance

The greatest amount of ions is formed by dissociation of 1 mole solution of:

5 mole of ions are formed by dissociation of 1 mole \(Al_2(SO_4)_3\)

\(Al_2(SO_4)_3 \leftrightarrow 2 Al ^{3+} + 3SO_4^{2-}\)

Amount of substance

The compound of type \(Na_2MO_4\) forms each element of two:

The correct answer is \(S, Cr\)

\(Na_2SO_4\)\(Na_2CrO_4\)

Amount of substance

Calculate the number of hydrogen molecules which occupy a volume of 5 liters of hydrogen (standard conditions).

The number of molecules: \(N = n* N_A, N_A = 6.02 * 10^{23} mol^{-1}\)

\(n=V/V_m, V_m = 22,4 l*mol^{-1}; n = 5/22,4 = 0,22 mol\).

\(N = 0,22* 6.02 * 10^{23} = 1,32*10^{23}\) molecules.

Amount of substance

Determine the amount of substance of sulfur oxide (IV), if its volume (standard conditions) was 28 liters. Enter that number in the answer field.

\(V_m = 22,4 l*mol^{-1}\)

\(n(SO_2) = V/V_m = 28/22,4 = 1,25 mol\)

 

Amount of substance

Molecular oxygen takes (standard conditions) volume 7.28 liters. Calculate the mass of gas. Enter that number in the answer field.

\(m(O) = n*A_r, V_m = 22,4 l*mol^{-1}, A_r(O) = 16 g* mol^{-1}, \)

\(n=V/V_m = 7,28/22,4 = 0,325 mol, \)

\(m(O) = 0,325* 16 = 5,2 g\)

 

Formulae

The compound composition \(K_2EO_3\) forms each of the two elements:

The correct answer is 2 (\(N, S\))

\(K_2NO_3, K_2SO_3\)

Formulae

What compounds exhibit the same degree of the oxidation of iron?

The correct answer is 1 (\(Fe^{2+}O, Fe^{2+}CO_3\)

Formulae

Among the presented substances: \(CH_4, H_2S, CH_3COOH, NH_3, H_5IO_6, K_2HPO_4\) acids are:

The correct answer is 2 (\(H_2S, CH_3COOH, H_5IO_6\))