Question

a comapny made magnesium by heating magnesium oxide with silicon: Si(s)+2MgO(s)+2Mg(s) . Calculate the mass of magnesium oxide needed to produce 4.8 tonnes pf magnesium

Answer 1

The  mass  of  MgO  needed to produce 4.8 tonnes of Mg   is
 8 tonnes  or 2,000 Kg  or 2,000 ,000 g

      calculation
Si  + 2 MgO  =  SiO2  +2 Mg


   step  1 :find the moles  of Mg


moles  =  mass/molar  mass
mass =  4.8 tonnes =  480,000  g
molar mass =  24 g/mol

moles  is therefore = 480,000 g/24g/mol = 200,000  moles

   then by use  of  mole  ratio  between   MgO to Mg  which is  1:1 therefore the moles  of MgO  is also = 200,000 moles

mass  of  MgO  =  moles of MgO x molar mass of MgO
molar mass  of MgO =  24 + 16 =40 g/mol

therefore the mass = 200,000 moles  x 40 g/mol  = 8,000,000 grams  or 8,000,000/1000= 8,000 Kg   or    8,000/1000  =  8  tonnes