Answer: 2:1
Step-by-step explanation:
First, we need to balance this equation because we are given one mole of Al and have that turn into two moles of Al (Likewise, two moles of O turn into three mol of O), which doesn't work out.
After balancing the equation, we are given 4 Al + 3 O2 -> 2 Al2O3. This makes sense because the number of moles of each element are the same on each side (4 Al -> 2 Al2 [4 Al], 6 O -> 2O3 [6O])
Because we are looking for the mole ratio of Al to Al2O3, we simply take the number of moles of Al (four) and divide that by the number of moles of Al2O3 (two) to get the least whole number for that ratio.
Hence, we get 4:2, which simplifies to 2:1