For the questions on this worksheet, consider the following equation: Ca(OH)2(s)

Question

For the questions on this worksheet, consider the following equation:

Ca(OH)2(s) + 2 HCl(aq) ? CaCl2(aq) + 2 H2O(l)

1) What type of chemical reaction is taking place?

2)         How many liters of 0.100 M HCl would be required to react completely with 5.00 grams of calcium hydroxide?

3)         If I combined 15.0 grams of calcium hydroxide with 75.0 mL of 0.500 M HCl, how many grams of calcium chloride would be formed?

4)         What is the limiting reagent from the reaction in problem #3?

5)         How many grams of the excess reagent will be left over after the reaction in problem 3 is complete?

Explanation / Answer

Convert the gram amount of Ca(OH)2:
5.00 g Ca(OH)2 (1 mol / 74.09 g Ca(OH)2) = 0.0675 mol Ca(OH)2

Find the mole ratio between the amount of OH- there is and Ca(OH)2 as a whole:
0.0675 mol Ca(OH)2 (2 mol OH- / 1 mol Ca(OH)2) = 0.135 mol OH-

So 5.00 g Ca(OH)2 releases 0.135 mol OH-. To neutralize 0.135 mol OH-, you need 0.135 mol H+. This is provided by HCl. You need 0.135 mol of HCl.

You have the concentration and the amount of moles you need, so you can find the amount in volume you need by the equation:

C * V = moles

0.100 M * V = 0.135 mol

V = 1.35 L

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