# A sample of seawater contains 0.000245 g of sodium chloride per mL of solution. How much sodium chloride is contained in 50.0 mL of this solution?

Oct 1, 2017

$0.01225 g$

#### Explanation:

Using Dimensional Analysis we can set up the correct equation to find the desired result. If we want mass (grams) from a concentration and volume it is this:
(g/(mL)) xx mL) = g

$0.000245 g \times 50.0 = 0.01225 g$

Oct 1, 2017

$\text{50 mL}$ of the given $\text{NaCl}$ solution contains $\text{0.0123 g}$ of $\text{NaCl}$.

#### Explanation:

This is basically a density problem, where the density is known:

$\text{0.000245 g/mL NaCl}$ solution.

In this question, the mass of $\text{NaCl}$ in $\text{50 mL}$ of solution is unknown.

$\text{density"="mass"/"volume}$

To find mass when density and volume are known, we can rearrange the density formula to isolate mass.

$\text{mass"="density"xx"volume}$

Plug in the known values and solve for mass.

50.0color(red)cancel(color(black)("mL NaCl sol'n"))xx(0.000245"g NaCl")/(1color(red)cancel(color(black)("mL NaCl sol'n")))="0.0123 g NaCl"=1.23xx10^(-2) "g NaCl" (rounded to three significant figures)