What is the weight percent of nacl in a solution made by dissolving 20 g of nacl in 200 ml of water

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What’s solution concentration?
What’s solution concentration in percent by mass?

Solution concentration can be expressed in many ways. However, here, we will discuss two ways in which solution concentration can be calculated. The two ways are:• Percent by mass• Molarity

What’s solution concentration?

Solution concentration is the amount of solute dissolved in a given amount of solution or solvent. Generally, we can express solution concentration mathematically as:Solution concentration = amount of solute/amount of solution or solvent

The solute is the chemical in lesser amounts, while the solvent is the chemical in larger amounts.

What’s solution concentration in percent by mass?

Percent by mass (% m) is the mass of solute divided by the mass of solution multiplied by 100. Mathematically, % by mass = (mass of solute in grams/mass of solution in grams) x 100.
Notice! Mass of solution = mass of solute in grams plus mass of solvent in grams.

Since the grams cancel out, the final unit will be in percent. For example, a 20.0 percent sodium chloride (NaCl) solution will contain 20.0 g of NaCl in 100 g of solution (20 g/100 g). Since mass of solution is equal to 100 g, we can get the mass of solvent by subtracting 20 g of solute from the 100 g of solution (100 g – 20 g = 80 g of solvent). So, if water was used as our solvent, our mass of water will be 80 g. This means that the 20 g of NaCl/80 g of water can be used as a conversion factor to convert from mass of solute to mass of solvent and vice versa.

For example,
How many grams of NaCl must be added to 1000 g
of water to prepare a 20.0 percent NaCl solution.

Answer

The 20 percent NaCl solution means 20 g of NaCl/100 g of solution (read as 20 g of NaCl in a 100 g of solution). Since the question demands how many grams of NaCl must be added to 1000 g of water, we have to figure out the amount of water in the 20 percent of solution so that we can set up the correct conversion factor. To get that, we simply subtract 20 g of NaCl from the 100 g of solution (100 g – 20 g = 80 g of water).
Now, our conversion factor is: 20 g NaCl/80 g water.

To figure out how many grams of NaCl must be added to 1000 g, we simply multiply the 1000 g of water by 20 g NaCl/80 g water. If this calculation confuses you, click here to read more about conversion factors.
Thus, 1000 g H2O x 20 g NaCl/80 g H2O = 250 g. Therefore, 250 g of NaCl must be dissolved in 1000 g of water to make a 20 % NaCl solution.

Here is a summary of the calculation:

Calculating mass of NaCl needed to make 20 % NaCl solution

To learn how to calculate solution concentration in Molarity, click here

Chemistry Solutions Percent Concentration

The percentage concentration of any solution is most commonly expressed as mass percent:

Mass % of any component of the solution =
(Mass of the component in the solution / Total mass of the solution) x 100

Other methods are:

Volume % of a component =
(Volume of the component/Total volume of the solution) x 100
1. Mass by volume percentage:
  It is the mass of solute dissolved in 100 mL of the solution.
i.e. Mass by Volume percentage =
(Mass of solute in grams/Volume of solution in mL) x 100

Here's a point to be kept in mind :
Whenever we say mass or volume of the solution, you need to add the respective masses and volumes of ALL the components of the solution. Do NOT commit the error of taking the mass or volume of only the solute or solvent in the denominators of the above expressions.

The concentration of a solution is most of the time expressed as the number of moles of solute present in 1 Liter of the solution (also called molarity )

(There are also other ways to express concentration. Please follow this link. )

EXAMPLE:
(a) If 25 moles of NaCl are present in 100 L of a solution wherein H2O is the solvent, then the concentration of the solution is #25/100=0.25 "mol·L"^-1#.

(b) What is the molarity of a solution prepared by dissolving 15.0 g of sodium hydroxide in enough water to make a total of 225 mL of solution?

Solution
- Calculate the number of moles of solute present.
Moles of NaOH = 15.0 g NaOH × #(1"mol NaOH")/(40.00"g NaOH")# = 0.375 mol NaOH
- Calculate the number of litres of solution present.
Volume = 225 mL × #(1"L")/(1000"mL")# = 0.225 L soln
- Divide the number of moles of solute by the number of litres of solution.
Molarity = #(0.375"mol")/(0.225"L")# = 1.67 mol/L
Let's address the question for both percent concentration by mass and for percent concentration by volume.

Percent concentration by mass is defined as the mass of solute divided by the total mass of the solution and multiplied by 100%. So,

#c% = m_(solute)/(m_(solution)) * 100%#, where

#m_(solution) = m_(solvent) + m_(solute)#

There are two ways to change a solution's concentration by mass
- Adding more solute - making the solution more concentrated;
- Adding more solvent - making the solution more dilute;
Let's take an example to better illustrate this concept. Say we dissolve 10.0g of a substance in 100.0g of water. Our concentration by mass will be

#c% = (10.0g)/(10.0g + 100.0g) * 100% = 9.09%#

Now let's try doubling the mass of the solute; the new concentration will be

#c% = (2 * 10.0g)/(2*10.0g + 100.0g) * 100% = 16.7%#

However, if we keep the mass of the solute at 10.0g and doubled the mass of the solvent (in this case, water), the concentration will be

#c% = (10.0g)/(10.0g + 2*100.0g) * 100% = 4.76%#

The same is true for percent concentration by volume, which is defined as the volume of the solute divided by the total volume of the solution and multiplied by 100%.

#c_(volume)% = V_(solute)/(V_(solute) + V_(solvent)) * 100%#

It's easy to see that manipulating either the volume of the solute or the volume of the solvent (or both) would change the solution's percent concentration by volume.
There are two types of percent concentration: percent by mass and percent by volume.

PERCENT BY MASS

Percent by mass (m/m) is the mass of solute divided by the total mass of the solution, multiplied by 100 %.

Percent by mass = #"mass of solute"/"total mass of solution"# × 100 %

Example

What is the percent by mass of a solution that contains 26.5 g of glucose in 500 g of solution?

Solution

Percent by mass =

#"mass of glucose"/"total mass of solution" × 100 % = (26.5"g")/(500"g")# × 100 % = 5.30 %

PERCENT BY VOLUME

Percent by volume (v/v) is the volume of solute divided by the total volume of the solution, multiplied by 100 %.

Percent by volume = #"volume of solute"/"total volume of solution"# × 100 %

Example

How would you prepare 250 mL of 70 % (v/v) of rubbing alcohol

Solution

70 % = #"volume of rubbing alcohol"/"total volume of solution" × 100 %# × 100 %

So

Volume of rubbing alcohol = volume of solution × #"70 %"/"100 %"# = 250 mL × #70/100#

= 175 mL

You would add enough water to 175 mL of rubbing alcohol to make a total of 250 mL of solution.