Question

II.

If there are 19 grams of oxygen in a sample of Aluminum oxide( A1203).
How many grams of Al are present?
III.
If there are 42 grams of hydrogen in a sample of pure Methane (CH4). How many grams of
carbon are present?

Answer 1

Mass of aluminium = 21.59 g

Mass of carbon = 124.98 g

Step-by-step explanation:

Part ii

Given data:

Mass of oxygen = 19 g

Mass of aluminium = ?

Solution:

Chemical equation:

4Al + 3O₂ → 2Al₂O₃

Now we will calculate the moles of oxygen.

Number of moles = mass / molar mass

Number of moles = 19 g/ 32 g/mol

Number of moles = 0.594 mol

Now we will compare the moles of oxygen and aluminium from balanced chemical equation,

O₂ : Al

3 : 4

0.594 : 4/3×0.594 = 0.8 mol

Mass of aluminium = moles × molar mass

Mass of aluminium = 0.8 mol × 26.982 g/mol = 21.59 g

Part iii

Given data:

Mass of hydrogen = 42 g

Mass of carbon = ?

Chemical equation:

C + 2H₂ → CH₄

Now we will calculate the moles of hydrogen.

Number of moles = mass / molar mass

Number of moles = 42 g/ 2.016 g/mol

Number of moles = 20.83 mol

Now we will compare the moles of hydrogen and carbon from balanced chemical equation,

H₂ : C

2 : 1

20.83 : 1/2 ×20.83 = 10.415 mol

Mass of carbon = moles × molar mass

Mass of carbon = 10.415 mol ×12 g/mol = 124.98 g