Photo AI
Deuterium (symbol D) is an isotope of hydrogen - VCE - SSCE Chemistry - Question 4 - 2005 - Paper 1
Question 4
Deuterium (symbol D) is an isotope of hydrogen. Water made from deuterium has the symbol D₂O and has similar properties to normal water. D₂O ionises according to the... show full transcript
Worked Solution & Example Answer:Deuterium (symbol D) is an isotope of hydrogen - VCE - SSCE Chemistry - Question 4 - 2005 - Paper 1
Step 1
Calculate the concentrations at equilibrium
Answer
From the equilibrium expression, we have:
K_a = rac{[D^+][OD^-]}{[D_2O]} = 1.82 imes 10^{-16}
In a neutral solution, the concentration of D⁺ ions will equal the concentration of OD⁻ ions. Thus, we can denote both concentrations as 'x'. Therefore:
K_a = rac{x imes x}{[D_2O]} = rac{x^2}{[D_2O]}
Given that pure D₂O has a concentration approximately equal to 55.5 M and considering a small value of x (change in concentration due to ionisation), we can say:
1.82 imes 10^{-16} = rac{x^2}{55.5}
Step 2
Step 3