Question

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

Answer 1

Answer:

Mass of MgO produced = 5.72 g

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 = $\frac{Mass\ in\ g}{Molar\ mass}$

No. of mol of Mg = $\frac{3.45}{24.305}=0.142 mol$

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

Answer 2

  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