Sand is converted to pure silicon in a three step process. the third step is sicl4(g) + 2mg(s) → 2mgcl2(s) + si(s) δh = –625.6 kj what is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon? multiple choice –7820 kj –25.0 kj –3.13 × 104 kj none of these choices are correct. –1.56 × 104 kj

The correct answer is -1.56 × 10⁴ KJ

Explanation:

SiCl₄ (g) + 2Mg (s) → 2MgCl₂ (s) + Si (s), the enthalpy change of the step is -625.6 KJ

From the mentioned reaction, one can see that 1 mole of SiCl₄ will generate 1 mole of Si, as there is a one to one relationship, thus, one can just multiply the enthalpy of the reaction with the number of moles. Therefore,  

Change in enthalpy = -625.6 KJ × 25 moles = -15640 KJ

Thus, the correct answer is -1.564 × 10⁴ KJ

hurricanes form when warm, moist air from the ocean surface quickly rises into the atmosphere and forms storm clouds and rain. when the clouds are formed, heat is released which warms the cool air in the upper regions of the atmosphere so that the cycle can continue. which two phases of the water cycle are repeated in this process?