A 150 ml solution of calcium hydroxide is titrated with 0.3 m hbr. what is the concentration of the original calcium hydroxide solution if it takes 200 ml of hbr to reach the equivalence point?

Chemistry
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A 150 mL solution of calcium hydroxide is titrated with 0.3 M HBr. What is the concentration of the original calcium hydroxide solution if it takes 200 mL of HBr to reach the equivalence point?

a. 0.2M b. 0.8 M c. 0.3 M d.0.7 M

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To find the concentration of the original calcium hydroxide solution, we can use the concept of stoichiometry and equivalence points in acid-base titrations.

In this case, we have a 150 ml solution of calcium hydroxide (Ca(OH)2) being titrated with 0.3 M hydrobromic acid (HBr), and it takes 200 ml of HBr to reach the equivalence point.

From the balanced chemical equation between calcium hydroxide and hydrobromic acid: Ca(OH)2 + 2HBr → CaBr2 + 2H2O, we can see that the ratio of the hydrobromic acid to calcium hydroxide is 2:1.

This means that for every 2 moles of HBr, we react with 1 mole of Ca(OH)2.

Since the concentration of HBr is 0.3 M and the volume used is 200 ml, we can calculate the moles of HBr used in the titration:

Moles of HBr = concentration * volume
= 0.3 M * 0.2 L
= 0.06 moles

According to the stoichiometry of the balanced equation, 1 mole of Ca(OH)2 is equivalent to 2 moles of HBr.

Therefore, the number of moles of Ca(OH)2 present in the original solution is: 0.06 moles * (1 mole Ca(OH)2 / 2 moles HBr) = 0.03 moles

To find the concentration of the original calcium hydroxide solution, we can use the formula:

Concentration = Moles / Volume

Substituting the values, we have:

Concentration = 0.03 moles / 0.15 L

Calculating this, the concentration of the original calcium hydroxide solution is 0.2 M.

Therefore, the correct answer is a. 0.2 M.

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