A solution of calcium bromide contains 20 g dm\(^3\). What is the molarity of the solution with respect to calcium bromide and bromide ions? [Ca = 40, Br = 80]
0. 1, 0 . 1
0. 1, 0. 2
0. 1, 0. 05
0.05, 0.1
Explanation
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20g/dm³ means 1 dm3 contains 20g
1 mole of CaBr2 contains 200g
20/200 = 0.1 mol
in 1 dm³ of soln = 0.1mol/dm³
CaBr2 > Ca2+ + 2Br-
0.1 0.1 0.2
= 0.1:0.2 B
First for CaBr2
Molarity=Molarconc./molar ass
Therefore the Molarity is 20/200=0.1
You know that for every 1mole of CaBr2, two miles of Br- ion is liberated. And after calculating the molarity of CaBr2 you will get 0.1.
Therefore
If 1mole of CaBr2 will liberate 2moles of Br- then
0.1mol/dm3 will liberate 0.2Mol/dm3
So I choose Option B.
Myschool please make the correction
Step 1: Molar mass of Calcium Bromide (CaBr₂)
The molar mass of calcium bromide can be calculated as:
Molar mass of CaBr₂=Ca+2×Br
Molar mass of CaBr₂=Ca+2×Br
=40+2×80=40+160=200 g/mol
=40+2×80=40+160=200g/mol
Step 2: Calculate the moles of CaBr₂
Given the concentration of the solution is 20 g/dm³, we can find the number of moles of CaBr₂ in 1 dm³ of the solution:
Moles of CaBr₂=Mass of CaBr₂Molar mass of CaBr₂=20 g200 g/mol=0.1 mol
Moles of CaBr₂=Molar mass of CaBr₂Mass of CaBr₂=200g/mol20g=0.1mol
So, the molarity of CaBr₂ is 0.1 M.
Step 3: Molarity of Bromide ions (Br⁻)
Since each formula unit of calcium bromide (CaBr₂) dissociates to produce 2 bromide ions (Br⁻), the molarity of bromide ions will be twice the molarity of CaBr₂.
Molarity of Br⁻=2×Molarity of CaBr₂=2×0.1=0.2 M
Molarity of Br⁻=2×Molarity of CaBr₂=2×0.1=0.2M
Final Answer:
Molarity of CaBr₂ = 0.1 M
Molarity of Br⁻ = 0.2 M
I needed an urgent explanation for this topic for better understanding and none was given
