Chapter 13 - The Chemistry of Solutes and Solutions - Questions for Review and Thought - Topical Questions - Page 605c: 50

0.1 M

Volume of teardrop=0.6 mL=$0.6\times10^{-3}\,L$ Mass of NaCl=4 mg= $4\times10^{-3}\,g$ Molar mass of NaCl=58.44 g/mol. Molarity of NaCl=$ \frac{Number\,of\,moles\,of\,NaCl}{Volume\, of\, solution\,in\,L}=\frac{\frac{Mass\,of\,NaCl}{Molar\,mass}}{Volume\,of\, solution\,in\,L}$ $=\frac{\frac{4\times 10^{-3}\,g}{58.44\,g/mol}}{0.6\times10^{-3}L}=0.1\,M$