Question

Определите степени окисления атомов элементов; укажите, какие реакции, уравнения которых приведены ниже, относятся в окислительно-восстановительным: а) CaCO3 2HCl = CaCl2 H2O CO2б) Mg 2HCl = MgCl2 H2 в) CaCO3 = CaO = CO2г) 2HgO = 2Hg O2

Answer 1

А) Не ОВР. Сl(-), Ca(2+), C(4+), O(2-), H(+).
б) ОВР. Mg(0)=>Mg(2+), H(+)=>H(0).
в) Не ОВР. Са(2+), С(4+), O(2-).
г) ОВР. Hg(2+)=>Hg(0), O(2-)=>O(0).

Answer 2

Oxidation States of Atoms:

To determine the oxidation states of atoms in a compound or equation, we need to consider the electronegativity and the number of valence electrons of each element. The oxidation state represents the charge that an atom would have if the compound or equation were ionic.

a) In the reaction CaCO3 + 2HCl = CaCl2 + H2O + CO2: - The oxidation state of Ca in CaCO3 is +2. - The oxidation state of C in CaCO3 is +4. - The oxidation state of O in CaCO3 is -2. - The oxidation state of H in HCl is +1. - The oxidation state of Cl in HCl is -1. - The oxidation state of Ca in CaCl2 is +2. - The oxidation state of Cl in CaCl2 is -1. - The oxidation state of H in H2O is +1. - The oxidation state of O in H2O is -2. - The oxidation state of C in CO2 is +4. - The oxidation state of O in CO2 is -2.

b) In the reaction Mg + 2HCl = MgCl2 + H2: - The oxidation state of Mg in Mg is 0. - The oxidation state of H in HCl is +1. - The oxidation state of Cl in HCl is -1. - The oxidation state of Mg in MgCl2 is +2. - The oxidation state of Cl in MgCl2 is -1. - The oxidation state of H in H2 is +1.

c) In the reaction CaCO3 = CaO + CO2: - The oxidation state of Ca in CaCO3 is +2. - The oxidation state of C in CaCO3 is +4. - The oxidation state of O in CaCO3 is -2. - The oxidation state of Ca in CaO is +2. - The oxidation state of O in CaO is -2. - The oxidation state of C in CO2 is +4. - The oxidation state of O in CO2 is -2.

d) In the reaction 2HgO = 2Hg + O2: - The oxidation state of Hg in HgO is +2. - The oxidation state of O in HgO is -2. - The oxidation state of Hg in Hg is 0. - The oxidation state of O in O2 is 0.

Oxidation-Reduction (Redox) Reactions:

An oxidation-reduction (redox) reaction involves the transfer of electrons between species. The species that loses electrons is oxidized, while the species that gains electrons is reduced.

a) The reaction CaCO3 + 2HCl = CaCl2 + H2O + CO2 is a redox reaction. Calcium (Ca) is oxidized from an oxidation state of +2 in CaCO3 to +2 in CaCl2, while hydrogen (H) is reduced from an oxidation state of +1 in HCl to +1 in H2O.

b) The reaction Mg + 2HCl = MgCl2 + H2 is not a redox reaction. Magnesium (Mg) does not change its oxidation state, and hydrogen (H) also does not change its oxidation state.

c) The reaction CaCO3 = CaO + CO2 is not a redox reaction. Calcium (Ca) and carbon (C) do not change their oxidation states.

d) The reaction 2HgO = 2Hg + O2 is a redox reaction. Mercury (Hg) is reduced from an oxidation state of +2 in HgO to 0 in Hg, while oxygen (O) is oxidized from an oxidation state of -2 in HgO to 0 in O2.

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