Question

you need to make 120.0 ml of a 0.65 m nacl solution. you have solid nacl and your lab partner has a 2.8 m nacl solution. explain how you each make the 0.65 m nacl solution.
(a) what mass of the solid nacl should you dissolve in pure water in order to prepare 120.0 ml of 0.65 m solution?
mass of nacl =
(b) what volume of 2.8 m nacl solution should your partner mix with pure water in order to prepare 120.0 ml of 0.65 m solution?
volume = ml
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Explanation:

Step1: Calculate the mass of NaCl for part (a)

The formula for molarity \(M=\frac{n}{V}\) (where \(n\) is the number of moles and \(V\) is the volume in liters). Rearranging for \(n = M\times V\).
Given \(M = 0.65\space M\) and \(V=120.0\space mL=0.120\space L\).
\(n = 0.65\times0.120 = 0.078\space mol\).
The molar mass of \(NaCl\) is \(M_{NaCl}=58.44\space g/mol\).
Using \(m=n\times M\), we have \(m = 0.078\times58.44\).
\(m=4.56\space g\).

Step2: Calculate the volume of \(2.8\space M\space NaCl\) for part (b)

Using the dilution formula \(M_1V_1 = M_2V_2\).
Here \(M_1 = 2.8\space M\), \(M_2=0.65\space M\), \(V_2 = 120.0\space mL\).
Rearranging for \(V_1=\frac{M_2V_2}{M_1}\).
\(V_1=\frac{0.65\times120.0}{2.8}\).
\(V_1 = 27.9\space mL\).

Answer:

(a) \(4.56\space g\)
(b) \(27.9\space mL\)