Answer:
To determine the empirical formula of the oxide, you can use the following steps:
Calculate the number of moles of water produced. In this case, there are 4g of water, which is equivalent to 4/18 = 0.22 moles of water.
Calculate the number of moles of the oxide. In this case, there are 5g of the oxide, which is equivalent to 5/molar mass = 0.3 moles of the oxide. (Note: You will need to know the molar mass of the oxide to complete this step. If it is not given, you will need to determine it by analyzing the oxide's elemental composition.)
Divide the number of moles of water by the number of moles of the oxide to determine the ratio of water to oxide. In this case, the ratio is 0.22/0.3 = 0.73.
Divide each element's ratio by the smallest ratio to determine the empirical formula. In this case, the ratio of water to oxide is 0.73, so you can divide this number by 0.73 to get a ratio of 1:1 for water and oxide. This means that the empirical formula of the oxide is H2O.
It is important to note that this method will only determine the empirical formula of the oxide, which represents the simplest whole number ratio of the elements in the compound. To determine the actual molecular formula of the compound, you will need to know the compound's molecular mass and compare it to the empirical formula.