Sand is converted to pure silicon in a three step process. the third step issicl4(g) + 2mg(s) ? 2mgcl2(s) + si(s) ? h = -625.6 kjwhat is the enthalpy change when 12.5 mol of silicon tetrachloride is converted to elemental silicon? a 12.5 kjb 3910 kjc 0.78 x 10^4 kjd 1.56 x 10^4 kj

(C) 0.78×10⁴ kJ

Explanation:

The enthalpy of the reaction = -625.6 kJ (Negative sign signifies heat released).

From the reaction,

1 mole of silicon tetrachloride undergoes reaction to produce 1 mole of elemental silicon with the release of energy 625.6 kJ

So,

For 12.5 moles of silicon tetrachloride:

The enthalpy is : -625.6 *12.5 kJ = 7820 kJ.

Rearranging in the form of answer as 7820 kJ = 0.78×10⁴ kJ (C)

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

jjj89t'ji; it hink the answer is your mom is not si