Question

A 3.00g of a certain Compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 192./gmol, is burned completely in excess oxygen, and the mass of the products carefully measured: product mass carbon dioxide 4.13g water 1.13g Use this information to find the molecular formula of X.

Answer 1

Answer: The molecular formula for the given organic compound X is
`C_6H_(8)O_7`

Step-by-step explanation:

We are given:

Mass of
`CO_2=4.13g`

Mass of
`H_2O=1.13g`

We know that:

Molar mass of carbon dioxide = 44 g/mol

Molar mass of water = 18 g/mol

For calculating the mass of carbon:

In 44g of carbon dioxide, 12 g of carbon is contained.

So, in 4.13 g of carbon dioxide, =
`(12)/(44)* 4.13=1.13g` of carbon will be contained.

For calculating the mass of hydrogen:

In 18g of water, 2 g of hydrogen is contained.

So, in 1.13 g of water,
`(2)/(18)* 1.13=0.125g` of hydrogen will be contained.

Mass of oxygen in the compound = (3.00) - (1.13+ 0.125) = 1.75 g

To formulate the empirical formula, we need to follow some steps:

Step 1: Converting the given masses into moles.

Moles of Carbon =
`\frac{\text{Given mass of Carbon}}{\text{Molar mass of Carbon}}=(1.13g)/(12g/mole)=0.094moles`

Moles of Hydrogen =
`\frac{\text{Given mass of Hydrogen}}{\text{Molar mass of Hydrogen}}=(0.125g)/(1g/mole)=0.125moles`

Moles of Oxygen =
`\frac{\text{Given mass of oxygen}}{\text{Molar mass of oxygen}}=(1.75g)/(16g/mole)=0.109moles`

Step 2: Calculating the mole ratio of the given elements.

For the mole ratio, we divide each value of the moles by the smallest number of moles

For Carbon =
`(0.094)/(0.094)=1`

For Hydrogen =
`(0.125)/(0.094)=1.33`

For Oxygen =
`(0.109)/(0.094)=1.16`

Step 3: Taking the mole ratio as their subscripts.

The ratio of C : H : O = 1: 1.33: 1.16

Converting them into whole number ratios by multiplying by 6:

The ratio of C : H : O = 6: 8: 7

Hence, the empirical formula for the given compound is
`C_6H_8O_7`

Empirical mass =
`6* 12+8* 1+7* 16=192g`

The equation used to calculate the valency is :

`n=\frac{\text{molecular mass}}{\text{empirical mass}}`

Putting values in above equation, we get:

`n=(192g/mol)/(192g/mol)=1`

Multiplying this valency by the subscript of every element of empirical formula, we get:

`C_6H_8O_7* 1=C_6H_(8)O_7`

Thus molecular formula for the given organic compound X is
`C_6H_(8)O_7`