Question

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

Answer 1

Concentration is 1 mole/liter

Step-by-step explanation:

Step 1: Determine the total number of moles of NaCl

`molarity = (moles)/(volume)`

`5.0 moles/liter = (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 = (moles)/(volume)`

`molarity = (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.