Ok lets write this firstly in a chemical equation ->
C6H12O6 + O2 -> H2O + CO2
Ok balance the equation.
C6H12O6 +6O2 -> 6H2O + 6CO2
Now both sides are balanced.
To see how many grams of oxygen are required to convert 23g of glucose we need to work in ratios and to work with ratios we need moles.
To convert moles divide by R.M.M (Relative Molecular Mass) of Glucose
6 C - 6 * 12
12 H - 12 *1
6 O - 6 * 16
-----------------
R.M.M = 180
23g / 180 = 0.127 moles of Glucose
C6H12O6 +6O2 -> 6H2O + 6CO2
The ratio between glucose and oxygen is 1:6 therefore for every glucose molecule we need 6 of oxygen.
0.127 moles * 6 = 0.762 moles of Oxygen
Now to find multiply by R.M.M. of O2
2 O * 2 *16 = 32
0.762 moles * 32 = 24.38 (rounded) grams of O2 required to convert Glucose to CO2 and H2O.
Hope this helps :D.
