Stoichiometry numerical ## Stoichiometry numerical-

Question 1) How many moles of N2 are needed to produce 8.2 moles of NH3 by the reaction of N2 & H2?

Solution –

N2(g)        +   3H2(g) –>     2NH3(g)

1 mole            3 mole             2 mole

2 mole NH3 is produced from = 1 mole N2

8.2 mole NH3 is produced from = 1x 8.2 / 2 mole N2= 4.1 mole N2

Moles of N2 are needed = 4.1 mole

Question 2) What weight of Zinc would be required to produce enough H2 to reduce completely 10.2 gm Copper (II) oxide to Copper?

Solution –

(a) CuO                           + H2    —->     Cu + H2O

63.5+16= 79.5 gm    1×2= 2gm

79.5 gm CuO requires H2 for reduction = 2 gm

10.2 gm CuO requires H2 for reduction = 2x 10.2 / 79.5 gm= 0.257 gm

mass of H2 required for reduction of CuO to Cu = 0.257 gm

(b) Zn         +   H2SO4     —–>    ZnSO4 +     H2

65 gm                                                                2 gm

2 gm H2 is produced from = 65 gm zinc

0.257 gm H2 is produced from = 65 x 0.257 /2.0 gm zinc = 8.3525 gm

Weight of Zinc required to produce 0.257 gm H2 = 8.35 gm

Question 3) Calculate the amount of KClO3 needed to supply sufficient oxygen for burning 112 L of CO gas at NTP.

Solution –

CO (g) + 1/2 O2(g) —–> CO2(g)

1 mole     1/2 = 0.5 mole

Volume of 1 mole CO at NTP = 22.4L

22.4 Litre of CO at NTP requires = 0.5 mole O2

112 Litre of CO at NTP requires = 0.5 x 112 / 22.4 mole O2

Moles of O2 = 2.5

2KClO3. —> 2KCl + 3O2

2 mole                           3 mole

3 moles O2 is produced from KClO3= 2 moles

2.5 moles O2 is produced from KClO3= 2 x 2.5 / 3.0 moles

Moles of KClO3 required = 1.67

molar mass of KClO3 = 39 + 35.5 + 16×3= 122.5 gm/mole

mass of KClO3 =  mole x molar mass= 1.67 x 122.5 = 204.575 gm

Mass of KClO3 needed = 204.58 gm

Stoichiometry numerical-

Question 4) 50.0 gm N2 & 10.0Kg of H2 are mixed together to produce NH3.Calculate the amount of NH3 produced in gm. Identify the limiting reagent.

Solution-

N2(g).   +.  3H2 (g) —-> 2NH3(g)

mole ratio    1 mole         3 mole             2 mole

molar mass of N2 = 14×2 = 28 gm/mole

molar mass of H2 = 1×2 = 2 gm/mole

molar mass of NH3 = 14+1×3 = 17 gm/mole

Moles of N2 = mass in gm/molar mass

= 50000/28

Moles of N2=1.786 x 103

Moles of H2 = mass in gm/molar mass

= 10000/2

Moles of H2=5.0 x 103

1 mole N2 reacts with = 3 mole H2

1.786 x 103 mole N2 reacts with =1.786 x 103 x 3 mole H2

Moles of H2 = 5.358 x 103

But we have only 5.0 x 103 Moles of H2, so H2 is limiting reagent.

3 moles H2 on reaction gives= 2 moles NH3

5.0 x 103 moles H2 on reaction gives= 2 x 5.0 x 103 / 3 moles NH3

Moles of NH3= 3.33 x 103

mass of NH3 = moles x molar mass =3.33 x 103 x 17= 56.61 x 103

Mass of NH3 = 56.61 x 103 gm = 56610 gm

Mass of NH3 = 56.61 Kg