A sample of an oxide of antimony (Sb) contained 25.0 g of antimony combined with 8.2 g of oxygen. The simplest formula for the oxide is?

Convert 25.0 g Sb to moles.

Convert 8.2 g oxygen to moles.
Find the ratio of one element to the other in small whole numbers. The easiest way to do that is to divide the smaller number of moles by itself. That assures a 1.000 for that numbers. Then divide the other by the same small whole number, round to whole numbers and that should be the empirical formula. [Note: In rounding to a whole number, be careful that you don't "round" too much; i.e., a 0.25 could become a whole number by multiplying everything by 4, a 0.5 could become a whole number by multiplying everything by 2, etc).

To determine the simplest formula for the oxide of antimony, we need to find the ratio of antimony to oxygen in the compound.

First, convert the given masses of antimony and oxygen to moles using their molar masses. The molar mass of antimony (Sb) is 121.8 g/mol, and the molar mass of oxygen (O) is 16.0 g/mol.

Moles of antimony:
moles of Sb = mass of antimony / molar mass of Sb
moles of Sb = 25.0 g / 121.8 g/mol = 0.205 mol

Moles of oxygen:
moles of O = mass of oxygen / molar mass of O
moles of O = 8.2 g / 16.0 g/mol = 0.513 mol

Next, divide the number of moles of each element by the smallest number of moles obtained. In this case, the smallest number of moles is 0.205 (moles of antimony).

Ratio of moles:
Sb:O = 0.205 mol / 0.205 mol : 0.513 mol / 0.205 mol
Sb:O = 1 : 2.51

To get whole numbers, multiply the ratio by the smallest possible integer that converts the ratio to whole numbers. In this case, multiply by 2 to get whole numbers for the ratio.

Simplest ratio:
Sb:O = 1 × 2 : 2.51 × 2
Sb:O = 2 : 5.02

Since the ratio of antimony to oxygen is approximately 2:5, the simplest whole-number ratio would be Sb2O5.

Therefore, the simplest formula for the oxide of antimony is Sb2O5.