A 40.0-mL sample of 0.100 M HNO2 is titrated with 0.200 M KOH. Calculate the volume required to reach the equivalence point (in mL)
HNO2 + KOH ==> KNO2 + H2O
mols HNO2 = M x L = ?
mols KOH = mols HNO2 from the balanced equation.
Then M KOH = mols KOH/L KOH.
You know M and mol KOH, solve for L and convert to mL.
To calculate the volume of KOH required to reach the equivalence point, we need to determine the stoichiometry of the reaction between HNO2 and KOH.
The balanced chemical equation for the reaction is:
HNO2 + KOH -> KNO2 + H2O
From the equation, we can see that it is a 1:1 ratio between HNO2 and KOH. This means that for every 1 mole of HNO2, we will require 1 mole of KOH.
First, let's calculate the number of moles of HNO2 in the 40.0 mL of 0.100 M HNO2 solution.
Number of moles = (volume in liters) x (concentration in M)
Number of moles of HNO2 = (40.0 mL) x (0.100 M) / 1000 mL/L
Number of moles of HNO2 = 0.004 mol
Since the stoichiometry is 1:1, we will require the same number of moles of KOH to reach the equivalence point.
Now, let's calculate the volume of KOH required to react with 0.004 moles. We'll use the molarity and the number of moles to calculate this.
Volume of KOH = (number of moles of KOH) / (concentration of KOH)
Volume of KOH = 0.004 mol / 0.200 M
Volume of KOH = 0.02 L = 20 mL
Therefore, the volume of KOH required to reach the equivalence point is 20 mL.
To calculate the volume required to reach the equivalence point during a titration, you need to use the concept of stoichiometry. Here's how you can do it step by step:
1. Write the balanced chemical equation for the reaction between HNO2 and KOH:
HNO2 + KOH → KNO2 + H2O
2. Determine the stoichiometry of the reaction. From the balanced equation, you can see that the stoichiometry is 1:1 between HNO2 and KOH. This means that 1 mole of HNO2 reacts with 1 mole of KOH.
3. Calculate the number of moles of HNO2 in the 40.0 mL sample:
Moles of HNO2 = Volume (in L) x Concentration (in mol/L)
Moles of HNO2 = 40.0 mL / 1000 mL/L x 0.100 mol/L
= 0.004 mol
4. Since the stoichiometry is 1:1 between HNO2 and KOH, the number of moles of KOH required to react completely with 0.004 mol of HNO2 is also 0.004 mol.
5. Now, use the concentration and the number of moles of KOH to calculate the volume required to reach the equivalence point:
Volume of KOH = Moles of KOH / Concentration of KOH
Volume of KOH = 0.004 mol / 0.200 mol/L
= 0.020 L
6. Finally, convert the volume from liters to milliliters:
Volume of KOH = 0.020 L x 1000 mL/L
= 20 mL
Therefore, the volume of 0.200 M KOH required to reach the equivalence point is 20 mL.