For the reaction of calcium with water, which of the following coefficients does the balanced equation have (using integer coefficients in their simplest ratio)? I) one, II) four, III) two. Is it A) I only, B) I and II only, C) I and III only, D) II and III only, or E) I, II, and III?
To answer this question, we need to create a balanced equation for the reaction of calcium with water. We know that the reactants of this equation are calcium and water. But what are the products? Calcium is a metal that’s found in group two of the periodic table. When metals react with water, it forms a metal hydroxide and a hydrogen gas. So, the products of this reaction are calcium hydroxide, which has the chemical formula Ca(OH)₂, and hydrogen gas, which is H₂. Now that we have the products and reactants of this reaction, we just need to balance our equation.
Right now, we have one calcium on each side of the reaction. We have two hydrogens in the reactants but four in the products, and one oxygen in the reactants but two in the products. Since we don’t have enough hydrogen or oxygen on the reactants side of our equation, let’s put a coefficient of two in front of the water. Now, we have four hydrogens on each side and two oxygens on each side. So, our equation is balanced.
If we look at the coefficients of our balanced equation, we have ones in front of the calcium, calcium hydroxide, and hydrogen gas. So, statement I is correct. We also have a two in front of the water. So, statement III is correct as well. We don’t have a four anywhere, so statement II is wrong. Statements I and III are correct, which matches answer choice C.