Question

1)Э+2H2O---->Э(OH)2+H22)Mg2Э+4HCl--->ЭН4 + 2 MgCl2 ( Это углерод?)3)2ЭS2+7O2---t--->2ЭO3+4SO2(газ)4)4KЭО4---t--->K2ЭO4+O2(Газ)+MnO2 ( марганец?)

Answer 1

В первой реакции любой щелочно-земельный металл типа кальция или магния,бария
во второй реакции я думаю это кремний
в третьей реакции  думаю что железо,только она должна быть записана так 4FeS+7O2=2Fe2O3+4SO2 
в четвертой марганец 

Answer 2

1) The equation you provided is a chemical equation that represents a reaction between a substance denoted as "Э" and water (H2O). The reaction produces a compound denoted as "Э(OH)2" and hydrogen gas (H2). However, I couldn't find any specific information about the substance denoted as "Э" in the search results.

2) The equation you provided represents a reaction between magnesium oxide (MgO) and hydrochloric acid (HCl). The reaction produces ammonia gas (NH3), magnesium chloride (MgCl2), and water (H2O). It does not involve carbon (C) as a reactant or product.

3) The equation you provided represents a reaction between sulfur dioxide (SO2) and oxygen (O2). The reaction produces ozone (O3) and sulfur trioxide (SO3) gas. It does not involve carbon (C) as a reactant or product.

4) The equation you provided represents a reaction between potassium permanganate (KMnO4) and heat. The reaction produces potassium manganate (K2MnO4), oxygen gas (O2), and manganese dioxide (MnO2). It does not involve carbon (C) as a reactant or product.

Please note that the information provided is based on the chemical equations you provided and the search results available. If you have any specific questions or need further clarification, feel free to ask.