As a result of the combustion of 9.6 g of metals in chlorine, 38 g of a metal chloride of the composition МеСL2 were obtained. Determine the metal Ме.
Let’s write the reaction equation:
Me + Cl2 = MeCl2;
We are given the mass of an unknown metal and the mass of the reaction product with the same metal. Let us express the quantities of mol (n) Me and MeCl2:
n (Me) = m (Me): M (Me) = 9.6 g: x g / mol (we take the unknown atomic mass of this metal for x).
n (MeCl2) = m (MeCl2): M (MeCl2) = 38 g: (x + 71) g / mol. (71 is the molar mass of Cl2 in MeCl2).
There are no coefficients in the reaction, which means we can equate the amounts of moles of Me and MeCl2:
9.6: x = 38: (x + 71);
We multiply our construction “crosswise” (if we write through a fraction, it will be clearer):
38x = (71 + x) * 9.6;
38x = 681.6 + 9.6x;
28.4x = 681.6;
x = 24.
A 24 is the atomic mass of Mg (according to the periodic table). Thus, Mg is the metal we were looking for.
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