Problem 86E
Solution Stoichiometry and Chemical Analysis (Section)
An 8.65-g sample of an unknown group 2A metal hydroxide is dissolved in 85.0 mL of water. An acid–base indicator is added and the resulting solution is titrated with 2.50 M HCl(aq) solution. The indicator changes color signaling that the equivalence point has been reached after 56.9 mL of the hydrochloric acid solution has been added
(a) What is the molar mass of the metal hydroxide?
(b) What is the identity of the metal cation: Ca2+, Sr2+, Ba2+?
Problem 86 E
Solution Stoichiometry and Chemical Analysis (Section)
An 8.65 -g sample of an unknown group 2 A metal hydroxide is dissolved in 85.0 mL of water. An acid-base indicator is added and the resulting solution is titrated with 2.50 M HCl ( aq ) solution. The indicator changes color signaling that the equivalence point has been reached after 56.9 mL of the hydrochloric acid solution has been added
(a) What is the molar mass of the metal hydroxide?
(b) What is the identity of the metal cation:
Step by Step Solution
Step 1 of 2
(a)
From the given,
Mass of unknown group 2A metal hydroxide = 8.65 g
It is dissolved in 85.0 mL of water, so the volume of this solution is 85.0 mL
When this solution is titrated with 2.50 M HCl(aq) solution, equivalence point is reached after
56.9 mL of the HCl(aq) solution is added.
So the moles of HCl required for neutralization is:
Moles of the hydrogen chloride are calculated by the following formula.
As group 2A metals (group 1A) form di-hydroxides, two moles of HCl is required to neutralize
one mole of hydroxide. Then the number of moles of metal hydroxide neutralized by 0.142 moles of HCl is
The molar mass of metal hydroxide is determined using its mass and moles
Therefore, the molar mass of metal hydroxide is 122 g/mol .
