Question

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

Answer 1

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

Answer 2

Mass of MgO produced = 5.72 g

Step-by-step explanation:

`2Mg + O_2 \rightarrow 2MgO`

Mass of Mg = 3.45 g

Molar mass of Mg = 24.305 g/mol

No. of mol of Mg =
`(Mass\ in\ g)/(Molar\ mass)`

No. of mol of Mg =
`(3.45)/(24.305)=0.142 mol`

From the reaction coefficient,

2 mol of Mg form 2 mol of MgO

So, 0.142 mol of Mg form 0.142 mol of MgO

Molar mass of MgO = 40.3044 g/mol

Mass of MgO in g = No. of mol × Molar mass

= 0.142 mol × 40.3044 g/mol

= 5.72 g