Al(s) + H2SO4(aq) → Al2(SO4)3(aq) + H2(g)
What is the coefficient of H2 in the balanced equation, obtained by using oxidation numbers?
2Al(s) + H2SO4(aq) → Al2(SO4)3(aq) + H2(g)
..0x2 = 0..2*1+ = 2.........2*3+ = 6..............0
multiply Al half by 1 and multiply H2SO4/H2 half by 3 to give
2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2(g)
To find the coefficient of H2 in the balanced equation using oxidation numbers, we need to determine the number of hydrogen atoms on both sides of the equation.
On the left-hand side, we have 2H atoms in the H2SO4(aq) compound.
On the right-hand side, we have only 1H2 molecule, which contains 2H atoms.
To balance the H atoms, we need to multiply H2 on the right-hand side by 2, which gives us:
Al(s) + H2SO4(aq) → Al2(SO4)3(aq) + 2H2(g)
Therefore, the coefficient of H2 in the balanced equation is 2.
To determine the coefficient of H2 in the balanced equation obtained by using oxidation numbers, we need to find the oxidation numbers of the elements involved in the reaction. The rules for assigning oxidation numbers are as follows:
1. The oxidation number of an element in its elemental form is always zero. In this case, the oxidation number of Al(s) is 0.
2. The sum of oxidation numbers in a neutral compound is always zero. The sulfate ion (SO4 2-) is a polyatomic ion with a charge of -2. Since there are three sulfate ions in the product Al2(SO4)3(aq), the total charge is -6. Therefore, the oxidation number of aluminum (Al) in Al2(SO4)3(aq) is +3 to balance out the negative charge.
3. The sum of oxidation numbers in a polyatomic ion is equal to the charge of the ion. The hydrogen sulfate ion (HSO4-) has a charge of -1. Since there is one H2SO4(aq) in the reactant, the total charge is -1. Therefore, the oxidation number of hydrogen (H) in H2SO4(aq) is +1.
Based on the above oxidation numbers, we can set up the equation:
2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + xH2(g)
Now, we need to balance the equation by ensuring that the number of atoms for each element is equal on both sides. Since there are 2 Al(s) atoms on the left side, we need 2 Al2(SO4)3(aq) molecules on the right side. This means we also need 3 H2(g) molecules on the right side to balance out the hydrogen atoms.
Therefore, the coefficient of H2 in the balanced equation obtained by using oxidation numbers is 3.