KHCO³ is contaminated with K²CO³ as impurity. If 2.5g of the impure KHCO³ on heating produces 0.224dm³ if CO² at s.t.p, calculate the percentage of K²CO³ impurity?
Since when does potassium carbonate decompose when heated?
To calculate the percentage of K₂CO₃ impurity, we need to find the mass of K₂CO₃ in the impure sample.
Given:
Mass of impure KHCO₃ = 2.5g
Volume of CO₂ produced at STP = 0.224 dm³
First, let's convert the volume of CO₂ to the number of moles. At STP, 1 mole of any ideal gas occupies 22.4 dm³.
Number of moles of CO₂ = Volume (dm³) / 22.4 dm³/mol
Number of moles of CO₂ = 0.224 dm³ / 22.4 dm³/mol
Number of moles of CO₂ = 0.01 mol
Now, let's find the molar ratio between KHCO₃ and CO₂. From the balanced chemical equation, 1 mole of KHCO₃ produces 1 mole of CO₂.
Number of moles of KHCO₃ = Number of moles of CO₂ = 0.01 mol
To find the molar mass of KHCO₃, we add up the molar masses of each element:
Molar mass of K = 39.10 g/mol
Molar mass of H = 1.01 g/mol
Molar mass of C = 12.01 g/mol
Molar mass of O = 16.00 g/mol
Molar mass of KHCO₃ = 39.10 + 1.01 + 12.01 + (3 * 16.00) = 100.11 g/mol
Now, let's find the mass of pure KHCO₃ in the impure sample using the number of moles:
Mass of pure KHCO₃ = Number of moles of KHCO₃ * Molar mass of KHCO₃
Mass of pure KHCO₃ = 0.01 mol * 100.11 g/mol
Mass of pure KHCO₃ = 1.0011 g
Finally, let's find the mass of K₂CO₃ impurity:
Mass of K₂CO₃ impurity = Mass of impure KHCO₃ - Mass of pure KHCO₃
Mass of K₂CO₃ impurity = 2.5 g - 1.0011 g
Mass of K₂CO₃ impurity = 1.4989 g
To calculate the percentage of K₂CO₃ impurity, we can use the formula:
Percentage of K₂CO₃ impurity = (Mass of K₂CO₃ impurity / Mass of impure KHCO₃) * 100
Percentage of K₂CO₃ impurity = (1.4989 g / 2.5 g) * 100
Percentage of K₂CO₃ impurity = 59.96%
Therefore, the percentage of K₂CO₃ impurity in the sample is approximately 59.96%.
To calculate the percentage of K₂CO₃ impurity in the given sample, we need to consider the stoichiometric ratio between KHCO₃ and CO₂.
The balanced chemical equation for the reaction is as follows:
2 KHCO₃(s) → K₂CO₃(s) + H₂O(g) + CO₂(g)
From the equation, we can see that 2 moles of KHCO₃ produce 1 mole of K₂CO₃.
First, let's calculate the number of moles of CO₂ produced from the given volume at standard temperature and pressure (s.t.p), which is 0.224 dm³.
1 mole of any gas at s.t.p occupies 22.4 dm³.
So, using the volume of CO₂, we can calculate the number of moles:
0.224 dm³ / 22.4 dm³/mol = 0.01 mol
Since the reaction has a 2:1 stoichiometric ratio between KHCO₃ and K₂CO₃, 1 mole of K₂CO₃ is equivalent to 2 moles of KHCO₃.
So, the number of moles of K₂CO₃ impurity can be calculated as follows:
0.01 mol CO₂ × (2 mol KHCO₃/1 mol CO₂) = 0.02 mol KHCO₃
Now, we can calculate the molecular weight of KHCO₃ and K₂CO₃ to find the percentage of K₂CO₃ impurity.
Molecular weight of KHCO₃ = 39.10 g/mol (K) + 1.01 g/mol (H) + 12.01 g/mol (C) + 16.00 g/mol (O)₃ = 100.10 g/mol
Molecular weight of K₂CO₃ = 39.10 g/mol (K) + 12.01 g/mol (C) + 16.00 g/mol (O)₃ = 138.21 g/mol
Now, let's calculate the mass of KHCO₃ in the impure sample:
m(KHCO₃) = 2.5 g - m(K₂CO₃)
To find the mass of K₂CO₃ in the impure sample, we can use the number of moles of K₂CO₃:
m(K₂CO₃) = 0.02 mol × 138.21 g/mol = 2.7642 g
Now, let's calculate the mass of KHCO₃:
m(KHCO₃) = 2.5 g - 2.7642 g = -0.2642 g
However, the calculated mass of KHCO₃ is negative. This means that the given data or calculations are incorrect. Please double-check the values and recalculate.