The following is given:
20 ml of HCl (2.0 M) added with
5 ml of Na2S2O3 (0.3 M) with
5 ml of H2O
S2O3^-2(aq) + 2H^+1 (aq) --> S (s) + SO2 (g) + H2O (l)
Calculate the following:
a) Reaction rate when 30 mg of sulphur is formed (in 30 ml of solution) after 55 seconds.
b) Rate of reaction in terms of (moles of thiosulphate ion) consumed per litre per second for the reacting solution.
To calculate the reaction rate and the rate of reaction in terms of moles of thiosulfate ion consumed per liter per second, we need to first determine the number of moles of reactants and products involved in the chemical reaction.
Let's start by calculating the number of moles of HCl, Na2S2O3, and S that are present in the given solution.
a) First, we need to find the number of moles of HCl (2.0 M) present in 20 ml of solution:
Moles of HCl = Volume (in liters) x Concentration
Moles of HCl = 20 ml / 1000 ml/L x 2.0 mol/L
Moles of HCl = 0.04 mol
Next, we need to find the number of moles of Na2S2O3 (0.3 M) present in 5 ml of solution:
Moles of Na2S2O3 = Volume (in liters) x Concentration
Moles of Na2S2O3 = 5 ml / 1000 ml/L x 0.3 mol/L
Moles of Na2S2O3 = 0.0015 mol
Since the stoichiometric coefficient of Na2S2O3 in the balanced chemical equation is 1, the number of moles of S formed will also be 0.0015 mol.
Now, we can calculate the reaction rate when 30 mg of sulfur is formed (in 30 ml of solution) after 55 seconds:
Reaction rate = Moles of S formed / Time
Reaction rate = (0.0015 mol / 0.03 L) / 55 s
Reaction rate = 0.0004545 mol/L/s
Therefore, the reaction rate when 30 mg of sulfur is formed (in 30 ml of solution) after 55 seconds is 0.0004545 mol/L/s.
b) To find the rate of reaction in terms of moles of thiosulfate ion consumed per liter per second, we need to consider the stoichiometric relationship between the thiosulfate ion (S2O3^-2) and the reacting solution.
From the balanced chemical equation, we can see that 1 mole of S2O3^-2 is consumed for the formation of 1 mole of S.
Since we know that 0.0015 mol of S is formed, it means that 0.0015 mol of S2O3^-2 is consumed.
Now, let's calculate the rate of reaction in terms of moles of thiosulfate ion consumed per liter per second:
Rate of reaction = Moles of S2O3^-2 consumed / Time
Rate of reaction = (0.0015 mol / 0.03 L) / 55 s
Rate of reaction = 0.0004545 mol/L/s
Therefore, the rate of reaction in terms of moles of thiosulfate ion consumed per liter per second for the reacting solution is 0.0004545 mol/L/s.