Question

1. how many grams of nacl (molar mass= 58 g/mol) are needed to prepare 100.ml of a 0.25m nacl solution?

a. 1500 g
b. 15 g
c. 5.8 g
d. 1.5 g

1. when methanol and water are mixed, they form a homogeneous mixture. based on the information in the table above, which of the following would be the best procedure for separating a mixture of methanol and water?

a. filtration
b. distillation
c. paper chromatography
d. column chromatography

1. which of the following methods is most appropriate to use to determine the number of different - colored components in a sample of black ink?

a. distillation at atmospheric pressure
b. elemental analysis to determine the mass ratio of c:h:n:o
c. column chromatography using a nonpolar stationary phase and water as the mobile phase
d. paper chromatography using different solvents with a range of polarities as the mobile phase

Explanation:

18.

Step1: Calculate moles of NaCl

Use the formula $n = M\times V$, where $M = 0.25\ M$ and $V=100\ mL = 0.1\ L$. So $n=0.25\ mol/L\times0.1\ L = 0.025\ mol$.

Step2: Calculate mass of NaCl

Use the formula $m=n\times M_m$, where $n = 0.025\ mol$ and $M_m = 58\ g/mol$. So $m = 0.025\ mol\times58\ g/mol=1.45\ g\approx1.5\ g$.

Methanol and water have different boiling - points. Distillation is used to separate components of a homogeneous mixture based on differences in boiling points. Filtration is for separating solids from liquids, and chromatography is for separating components based on different affinities for stationary and mobile phases.

Paper chromatography with solvents of different polarities can separate different - colored components in ink based on their different solubilities and migration rates in the mobile phase. Distillation is for separating based on boiling points, elemental analysis is for determining elemental composition, and column chromatography with a non - polar stationary phase and water as the mobile phase may not be the best for ink separation.

Answer:

D. 1.5 g

19.