Final answer:
The correct coefficient for blank 2 in front of the H2 in the equation C + ____H2 → CH4 is 2. This balances the equation as it ensures that there are 4 hydrogen atoms on both sides.
Step-by-step explanation:
To determine the coefficient for blank 2 (in front of the H2) in the equation C + ____H2 → CH4, we must ensure that the number of atoms for each element is the same on both sides of the equation. Since there are 4 hydrogen atoms in one molecule of CH4, we need to balance the equation by adding a coefficient of 2 in front of the formula for hydrogen (H2). Doing so, the balanced equation will be:
C(s) + 2H2(g) → CH4(g)
The coefficient of 2 in front of H2 indicates that there are 2 molecules of diatomic hydrogen, summing up to a total of 2 × 2 = 4 atoms of hydrogen, which matches the 4 hydrogen atoms present in one molecule of methane (CH4).