Explain the effect of pressure on the following chemical equation :
2. Explain the effect of concentration in the following equation :
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Explanation:

One

Pressure will favor the side with the least number of mols if it the larger number of moles counts only the gases. (Le Chetalier's Principle). In this case both CaCO3 and CaO are not soluble in water. The only gas is CO2. Since it represents the most number of mols the reactant is favored.

More or Less are very troublesome words in beginning science. Make sure you understand their meaning for this question. The more pressure applied, the more the reactants will be favored and the equation shifts left.

Two

Fe and Fe3O4 are both solids. It depends on the form that water takes. Looking it up, it is shown to be in a gas form. That means if you increase the pressure, nothing will happen. That is not your question, but you should note it.

The answer to your question is you increase the concentration of Fe or H2O, the equilibrium will shift right.

If you add more Fe3O4 or hydrogen it will shift left.

Chemists say that if you alter the equilibrium the equation will shift in the opposite direction to compensate for the action you have taken.