Question

A 5.203-g sample of calcium is burned in air to produce a mixture of two ionic compounds, calcium oxide and calcium nitride. Water is added to this mixture. It reacts with calcium oxide to form 4.768 g of calcium hydroxide.

How many grams of calcium oxide are formed?
How many grams of calcium nitride?

Answer 1

Mass of CaO formed = 3.6106 g

Mass of
`Ca_3N_2` formed = 6.4170 g

Step-by-step explanation:

The chemical reaction is shown below as:-

`Ca+O_2\rightarrow 2CaO`

It will react with
`H_2O` and forms
`Ca(OH)_2`. The reaction is shown below as:-

`CaO+H_2O\rightarrow Ca(OH)_2`

Overall reaction is;-

`Ca+O_2+2H_2O\rightarrow 2Ca(OH)_2`

Let the mass of
`Ca` reacted to form
`CaO` = x g

Molar mass of
`Ca` = 40.078 g/mol

Moles of
`Ca`=
`(x)/(40.078)` moles

From the reactions shown above:-

1 mole of
`Ca` on reaction forms 2 moles of
`Ca(OH)_2`

Thus,

`(x)/(40.078)` mole of
`Ca` on reaction forms
`(2x)/(40.078)` moles of
`Ca(OH)_2`

Moles of
`Ca(OH)_2` =
`(2x)/(40.078)` moles

Molar mass of
`Ca(OH)_2` = 74.093 g/mol

Mass of
`Ca(OH)_2` = Moles*Molar mass =
`(2x)/(40.078)* 74.093` g

Also, given that mass of
`Ca(OH)_2` produced = 4.768 g

Thus,

`(2x)/(40.078)* 74.093=4.768`

x = 1.2895 g

Thus, mass of
`Ca` reacted to form
`CaO` = 1.2895 g

Mass of
`Ca` reacted to form
`Ca_3N_2` = 5.203g - 1.2895 g = 3.9135 g

Thus,

`Ca+O_2\rightarrow 2CaO`

40 g of Ca on reaction forms 112 g of CaO

So,

1 g of Ca on reaction forms 112/40 g of CaO

1.2895 g of Ca on reaction forms
`(112)/(40)* 1.2895` g of CaO

Mass of CaO formed = 3.6106 g

Also,

`3Ca+N_2\rightarrow Ca_3N_2`

120 g of Ca on reaction forms 148 g of
`Ca_3N_2`

So,

1 g of Ca on reaction forms 148/120 g of
`Ca_3N_2`

5.203 g of Ca on reaction forms
`(148)/(120)* 5.203` g of
`Ca_3N_2`

Mass of
`Ca_3N_2` formed = 6.4170 g