A solution of Ba(OH)2 is titrated into a solution of HOBr.
(i) Calculate the volume of 0.115 M Ba(OH)2(aq) needed to reach the equivalence point when
titrated into a 65.0 mL sample of 0.146 M HOBr(aq).
(ii) Indicate whether the pH at the equivalence point is less than 7, equal to 7, or greater than
A solution of Ba(OH)2 is titrated into a solution of HOBr.
(i) Calculate the volume of 0.115 M Ba(OH)2(aq) needed to reach the equivalence point when
titrated into a 65.0 mL sample of 0.146 M HOBr(aq).
(ii) Indicate whether the pH at the equivalence point is less than 7, equal to 7, or greater than
We can start by writing the balanced chemical equation for the reaction between Ba(OH)2 and HOBr:
Ba(OH)2 + 2 HOBr → Ba(Br)2 + 2 H2O
From the equation, we can see that the stoichiometry of the reaction is 1:2 between Ba(OH)2 and HOBr. This means that for each mole of Ba(OH)2 used, we will need 2 moles of HOBr.
(i) To find the volume of Ba(OH)2 we need, we can use the following equation:
n(HOBr) = C(HOBr) x V(HOBr)
where n is the number of moles of HOBr, C is the concentration of HOBr, and V is the volume of HOBr used. We can rearrange this equation to solve for V:
V(HOBr) = n(HOBr) / C(HOBr)
We know that at the equivalence point, the number of moles of Ba(OH)2 added will be equal to the number of moles of HOBr present in the sample. Since we have 65.0 mL of 0.146 M HOBr, we can calculate the number of moles of HOBr:
n(HOBr) = C(HOBr) x V(HOBr) = 0.146 mol/L x 0.0650 L = 0.00949 mol
Therefore, at the equivalence point, we will need half as many moles (0.00475 mol) of Ba(OH)2. The concentration of Ba(OH)2 is given as 0.115 M, so we can find the volume of Ba(OH)2 needed using the same equation as before:
V(Ba(OH)2) = n(Ba(OH)2) / C(Ba(OH)2) = 0.00475 mol / 0.115 mol/L = 0.0413 L = 41.3 mL
So we need 41.3 mL of 0.115 M Ba(OH)2 to reach the equivalence point.
(ii) At the equivalence point, all the HOBr will have reacted with the Ba(OH)2 to form a salt (Ba(Br)2) and water. Since HOBr is a weak acid and Ba(OH)2 is a strong base, the pH at the equivalence point will be greater than 7 (basic).
To answer this question, we need to determine the balanced chemical equation for the reaction between Ba(OH)2 and HOBr, and then calculate the volume of Ba(OH)2 needed to reach the equivalence point.
The balanced chemical equation for the reaction between Ba(OH)2 and HOBr is:
Ba(OH)2(aq) + 2 HOBr(aq) -> Ba(Br)2(aq) + 2 H2O(l)
(i) To find the volume of Ba(OH)2 needed to reach the equivalence point, we can use the stoichiometry of the balanced equation.
Step 1: Calculate the moles of HOBr in the 65.0 mL sample:
Moles of HOBr = concentration x volume
Moles of HOBr = 0.146 M x 0.0650 L
Moles of HOBr = 0.00949 mol
Step 2: Use the stoichiometry of the balanced equation to find the moles of Ba(OH)2 required:
From the balanced equation, we can see that 1 mole of Ba(OH)2 reacts with 2 moles of HOBr. Therefore, moles of Ba(OH)2 = (1/2) x moles of HOBr
Moles of Ba(OH)2 = (1/2) x 0.00949 mol
Moles of Ba(OH)2 = 0.00475 mol
Step 3: Calculate the volume of 0.115 M Ba(OH)2 solution needed to provide 0.00475 mol of Ba(OH)2:
Volume of Ba(OH)2 = moles/concentration
Volume of Ba(OH)2 = 0.00475 mol / 0.115 M
Volume of Ba(OH)2 = 0.0413 L or 41.3 mL
(ii) At the equivalence point, the reaction is complete and all the reactants have been converted to products. In this case, Ba(Br)2 and water are the products. Since water is a neutral substance, the pH at the equivalence point will be determined by the dissociation of Ba(Br)2. Ba(Br)2 is a salt of a strong base (Ba(OH)2) and a weak acid (HOBr). Therefore, the pH at the equivalence point will be greater than 7.
To solve this problem, we need to use the concept of stoichiometry and the balanced chemical equation for the reaction between Ba(OH)2 and HOBr. The balanced chemical equation is:
2 HOBr + Ba(OH)2 -> Ba(Br)2 + 2 H2O
(i) To determine the volume of Ba(OH)2 needed to reach the equivalence point, we can use the stoichiometry of the reaction and the given concentrations and volumes.
Step 1: Write down the balanced chemical equation.
2 HOBr + Ba(OH)2 -> Ba(Br)2 + 2 H2O
Step 2: Determine the number of moles of HOBr from the concentration and volume.
moles of HOBr = concentration × volume = 0.146 M × 65.0 mL
Step 3: Use the stoichiometry of the balanced chemical equation to determine the moles of Ba(OH)2 needed.
From the balanced chemical equation, we see that 2 moles of HOBr react with 1 mole of Ba(OH)2.
Therefore, moles of Ba(OH)2 = 0.5 × moles of HOBr
Step 4: Convert the moles of Ba(OH)2 to volume using its concentration.
volume of Ba(OH)2 = moles of Ba(OH)2 / concentration of Ba(OH)2
(ii) To determine the pH at the equivalence point, we need to consider the reaction between Ba(OH)2 and HOBr. Ba(OH)2 is a strong base, while HOBr is a weak acid. Hence, the reaction will produce a basic solution.
Since Ba(OH)2 is a strong base, it will fully dissociate into Ba2+ and OH- ions. The OH- ions will react with the HOBr to form water (neutralization reaction). As a result, the pH at the equivalence point will be greater than 7, indicating a basic solution.
Note: To obtain the exact pH value at the equivalence point, additional information such as the pKa value of HOBr is required.