Biochem- Amino- Acids - Lecture notes 1, Study notes of Chemistry

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CONCENTRATION OF SOLUTION

What does Tang juice tastes like if you don’t put much powder?

What does Tang juice tastes like if you put too much powder? Too little?

DILUTE SOLUTION

• contains small amount of solute dissolved compared to the solvent. CONCENTRATED SOLUTION
• contains large amount of solute compared to the amount of solvent.
• (^) SATURATED SOLUTION
• contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.
• (^) UNSATURATED SOLUTION
• contains less solute than it has the capacity to dissolve.
• (^) SUPERSATURATED SOLUTION
• contains more solute than is present in a saturated solution.

PERCENT BY MASS AND PERCENT BY VOLUME  The percentage concentration of a solution may be expressed in two ways, by mass or by volume. Percent by mass= mass of solute/mass of solution x 100% Percent by volume= vol. of solute/vol of solution x 100%

2. What is the percentage by mass of a solution made by dissolving 2.0 g sugar in 150 mL water?

ACTIVITY # 6 – concentration of

solution

1. Calculate the concentration

of solution (in percent) of

the following:

a. 9.0 g of salt in 100.0 g of

solution

b. 5.0 mL of alcohol in 20 mL

of water

Answers:

a. 9 g/ 100 g (100%) = 9 % salt b. 5 ml/ 25 ml (100 %) = 20% alcohol 2.) 0.892 g/ 55.492 (100%) = 1.61% KCl 3.) 12g/ 262g (100%) = 4.58% salt

PARTS PER MILLION (ppm)

 Is a unit for expressing very dilute concentrations.  (^) It is commonly used to express the concentration of pollutants in air or in water. Components of gas mixtures present in very small amounts are usually expressed in ppm by volume as defined by the equation. ppm of component = vol of component/total vol of solution x 10 6 ppm

Answer

ppm = vol of pure gas/total vol of gas

mixture (10^6 ppm)

= 0.0060 L/100 L x 10^6 ppm

= 60 ppm CO

MOLARITY

-defined as the number of moles of solute per liter of solution. Molarity = number of moles of solute / liter of solution UNIT: mol/L or M

Answer

1. 0.05 M

2. 0. 22 M

MOLALITY

 Is the number of moles of solute dissolved in 1kg of solvent. Molality = moles of solute/ mass of solvent UNIT: mole/kg or m

Quiz # 1

1. What is the molality of a solution containing 7.78 g urea (NH 2 ) 2 CO in 203 g of water?
2. Calculate the molar concentration of a solution prepared by dissolving 0.5 g AgNO 3 in 100mL of water. Assume that the volume is constant.
3. How many grams of CuSO 4 must be dissolved in 250 mL of water to make a 0.10 M solution?
4. If 1000 g of water from Luboc River contains 0. 0075 g of Ca2+^ ion, how many ppm by mass of Ca2+^ is present in Luboc River?
5. A sample of 0.95 g of magnesium chloride is dissolved in 45.7 g of water. What is the percent by mass of MgCl 2 in the solution?

6. A solution is prepared by dissolving 4.00 g of NaOH in 100.00 g of water. The volume of the resulting solution is 102.00 mL. Calculate the following: a. Mole fraction of NaOH b. Molarity of the solution c. Molality of the solution d. Mass percent of NaOH e. Density of the solution