Chapter 15, Problem 60A

Interpretation Introduction

Interpretation: The solutions need to be arranged from most concentrated to least concentrated.

Concept introduction: Molarity can be defined as the number of moles of solute in 1 liter of solution. Thus,

  $\text{Molarity(}M\text{)}=\frac{\text{Number of moles of solute}}{\text{Volume of the solution in litre}}$

Now, $\text{Number of moles of solute}\propto$ number of molecules

Hence $\text{Molarity}\propto \frac{\text{Number of molecules of solute}}{\text{Volume of the solution in litre}}$

So greater the molarity more concentrated is the solution.

Answer to Problem 60A

Correct decreasing concentration order: solution A > solution D > solution C > solution B.

Explanation of Solution

For solution A $\text{Molarity}\propto \frac{\text{4}\text{.0 molecules}}{1.0\text{ L}}\propto 4.0\text{ molecules / L}$

For solution B $\text{Molarity}\propto \frac{\text{6}\text{.0 molecules}}{4.0\text{ L}}\propto 1.5\text{ molecules / L}$

For solution C $\text{Molarity}\propto \frac{\text{4}\text{.0 molecules}}{2.0\text{ L}}\propto 2.0\text{ molecules /}\text{ L}$

For solution D $\text{Molarity}\propto \frac{\text{6}\text{.0 molecules}}{2.0\text{ L}}\propto 3.0\text{ molecules / L}$

Conclusion

Correct decreasing concentration order: solution A > solution D > solution C > solution B.