A 1.00 L volume of HCl reacted completely with 2.00 L of 1.50 M Ca(OH)₂ according to the balanced chemical equation below:

[tex]\[2 \text{HCl} + \text{Ca(OH)}_2 \rightarrow \text{CaCl}_2 + 2 \text{H}_2\text{O}\][/tex]

What was the molarity of the HCl solution?

A. 0.375 M
B. 1.50 M
C. 3.00 M
D. 6.00 M



Answer :

To find the molarity of the [tex]\( HCl \)[/tex] solution, we can follow these steps:

1. Write the balanced chemical equation:
[tex]\[ 2 HCl + Ca(OH)_2 \rightarrow CaCl_2 + 2 H_2O \][/tex]
According to the equation, 2 moles of [tex]\( HCl \)[/tex] react with 1 mole of [tex]\( Ca(OH)_2 \)[/tex].

2. Determine the moles of [tex]\( Ca(OH)_2 \)[/tex]:
We are given that the volume of [tex]\( Ca(OH)_2 \)[/tex] is 2.00 [tex]\( L \)[/tex] and its molarity is 1.50 [tex]\( M \)[/tex]. We can calculate the moles of [tex]\( Ca(OH)_2 \)[/tex] using:
[tex]\[ \text{Moles of } Ca(OH)_2 = \text{Molarity} \times \text{Volume} = 1.50 \, M \times 2.00 \, L = 3.00 \text{ moles } \][/tex]

3. Calculate the moles of [tex]\( HCl \)[/tex] needed:
From the balanced equation, we see that 2 moles of [tex]\( HCl \)[/tex] react with 1 mole of [tex]\( Ca(OH)_2 \)[/tex]. Therefore, the moles of [tex]\( HCl \)[/tex] needed are:
[tex]\[ \text{Moles of }HCl = 2 \times \text{Moles of } Ca(OH)_2 = 2 \times 3.00 \text{ moles} = 6.00 \text{ moles} \][/tex]

4. Calculate the molarity of the [tex]\( HCl \)[/tex] solution:
We are given that the volume of the [tex]\( HCl \)[/tex] solution is 1.00 [tex]\( L \)[/tex]. Molarity is defined as the number of moles of solute per liter of solution. Therefore, the molarity of [tex]\( HCl \)[/tex] is:
[tex]\[ \text{Molarity of } HCl = \frac{\text{Moles of } HCl}{\text{Volume in liters}} = \frac{6.00 \text{ moles}}{1.00 \text{ L}} = 6.00 \, M \][/tex]

So, the molarity of the [tex]\( HCl \)[/tex] solution is [tex]\( 6.00 \, M \)[/tex].

Answer:
The correct answer is [tex]\( 6.00 \, M \)[/tex].

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