Question

If 100. ml of water is added to 25 ml of 5.0 m nacl, the final concentration is __________.

Answer 1

Answer:

Concentration is 1 mole/liter

Explanation:

Step 1: Determine the total number of moles of NaCl

$molarity = \frac{moles}{volume}$

$5.0 moles/liter = \frac{moles}{0.025 liter}$

$moles = 0.125 moles$

Step 2: Determine the total volume

$Volume_{total} =Volume_{water}+Volume_{solution}$

$Volume_{total} =0.1+0.025$

$Volume_{total} =0.125 liter$

Step 3: Determine molarity

$molarity = \frac{moles}{volume}$

$molarity = \frac{0.125}{0.125}$

$molarity = 1 mole/liter$

Answer 2

We may apply a mass balance here. The total moles of NaCl will remain constant before and after the mixing of the solutions. We have three solutions:
1) 25 ml of 5 M NaCl
2) 100 ml of 0 M NaCl
3) A mixture of these solutions with volume 125 ml and concentration C

The moles of a substance are equal to the product of the concentration and volume. Thus:

25 * 5 + 100 * 0 = 125 * C
C = 1 M

The concentration of the final solution is 1 M.