The answer has to depend on the mass of the copper that you're trying to melt.
But there is a formula which you can calculate the energy required if you have the information of the mass. This formula requires the value called specific latent heat of fusion, which is the energy required to melt or freeze a specific mass of copper without changing its temperature but change its state.

E is the total energy required, m is the mass, and lv is the specific latent heat of fusion of copper.
Usually, in questions, lv is given. But we can also look it up online which is around 205kJ kg^-1
this means, to melt or freeze a copper, we need to work the mass multiplied by 205kJ in order to calculate its total energy needed or released.
Answer:-
KOH determines how much Mg(OH)2 is made.
2 mol of Mg(OH)2 formed
Explanation:-
The balanced equation is
MgCl2 + 2KOH --> Mg(OH)2+ 2KCI,
From seeing the coefficients we notice
2 mol of KOH reacts with 1 mol of MgCl2
4 mol of KOH reacts with 1 x 4 / 2 = 2 mol of MgCl2
3 moles of MgCl2 was added but only 2 mol react.
So we see there is excess MgCl2 .
Hence KOH is the limiting reactant.
So KOH determines how much Mg(OH)2 is made.
We see from the balanced chemical equation,
2 mol of KOH gives 1 mol of Mg(OH)2.
4 mol of KOH will give 1 x 4 /2 = 2 mol of Mg(OH)2.
The gases like nitrogen and oxygen are not greenhouse gases because they do not absorb infrared radiation.
<h3>What are Greenhouse gases?</h3>
Greenhouse gas is a gas that has the property of absorb infrared radiation from the Earth’s surface and reradiate back to the Earth’s surface, thus contributing to the greenhouse effect.
<h3>What is infrared radiation?</h3>
Infrared radiation is an electromagnetic radiation with wavelengths longer than those of visible light.
Carbon dioxide, nitrous oxide, methane, and water vapour are the most important greenhouse gases.
Hence, nitrogen and oxygen are not greenhouse gases despite being in the atmosphere.
To learn more about greenhouse gas here
brainly.com/question/27590185
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