If 3.45 grams of Mg are burned how many grams of MgO are produced

The number of grams of Mgo that are produced is calculated as follows

calculate the moles of Mg used

that is moles = mass/molar mass

= 3.45 g / 24.305g/mol = 0.142 moles

write the equation for reaction

that is 2 Mg + O2 = 2 MgO

by use of mole ratio between Mg to Mgo which is 2:2 this implies that the moles of Mgo is also 0.142 moles

mass of Mgo = moles x molar mass of MgO

molar mass of Mgo = 24.305 + (3x15.999) = 72.302 g/mol

mass = 0.142 mol x 72.302 g/mol = 10.27 grams