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Concentration is the measure of the amount of solute within a unit of solvent. For a solution, chemists often go by liters. Note: the volume of solution usually considers the volume of the solute and the solvent combined. For example, if you combine 5 marbles with a beaker of water (solvent), the total volume would be 0.5 liters. The concentration of the marbles in the water would be 5 marbles / 0.5 liters = 10 marbles per liter. Of course, marbles don't dissolve in water, but they serve to illustrate that it's not just the solvent that contributes to the solution. The volume of solute molecules are much smaller than marbles, so we count them not by the dozen, but by the mole, which is an astronomically large number (6.02 * 10^23). This many molecules have a mass of 342 grams. If a chemist drops 684 grams of sugar into a beaker of water and it dissolves, what is the molarity of the solution? (moles of solute / volume of solution in liters) In the language of chemistry, "moles per liter" concentration is also called "molar". So when a chemist wants to know the concentration of a solution, she'll ask "What's the molarity?" Now, what is the molarity of the following solutions? (1.9 M, 3.5 M, 2.3 M) Molarity is usually abbreviated with a capital M. So a 42 M solution of sugar water may be expressed as 42M. So how many grams of sugar are there in a 42 M solution of sugar water? Please explain. There are two things you need to know in order to calculate the amount of solute in a solution. What are these two things?
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Molarity is defined as moles of solute per liter of solution. It tells you the concentration of the solute in the solution. Show more…
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Calculate the concentration in moles per liter (M) of a solution that contains 0.517 mol CuSO4 and has a volume of 0.725 L. concentration = M Calculate the concentration in moles per liter (M) of a solution that contains 0.798 mol NiCl2 and has a volume of 0.365 L. concentration = M Calculate the concentration in moles per liter (M) of a solution that contains 0.250 mol K2Cr2O4 and has a volume of 0.880 L. concentration = M Isopropyl alcohol is mixed with water to produce a 36.0% (v/v) alcohol solution. How many milliliters of each component are present in 795 mL of this solution? Assume that volumes are additive. alcohol: mL water: mL The mass of solute per 100 mL of solution is abbreviated as (m/v). Mass is not technically the same thing as weight, but the abbreviation (w/v) is also common. How many grams of sucrose are needed to make 745 mL of a 34.0% (w/v) sucrose solution? mass: g sucrose How many milliliters of a 0.900% normal saline solution can be prepared from 4.00 g of sodium chloride, NaCl? Note that mass is not technically the same as weight, but the abbreviation % (w/v) is often used interchangeably with % (m/v). volume: mL A 1939 g sample of ground water is found to contain 0.0581 g of arsenic. Calculate the concentration of arsenic in parts per million, ppm. concentration: ppm
Sri K.
Molarity is defined as the number of moles per liter of solution (mol/L or M). The mass of a mole is equal to the atomic mass or molecular weight of the substance, expressed in grams/mole or daltons (gram molecular weight). Molecular weight is obtained by adding the atomic weights of each atom in the molecule. What is the molecular weight of glucose (C6H12O6)? (Atomic weights: carbon = 12, hydrogen = 1, oxygen = 16). Remember not to confuse molarity with molality, which is the number of moles of solute in kg of solvent (not total solution). The density of water is 1.00 g/ml, thus 1 kg of water occupies a volume of 1 liter. Therefore, to make a molar (M) solution of NaCl, you would take 1 mole of NaCl and add sufficient water to make a final total volume of 1 liter. To make a molal (m) solution, you would simply add 1 liter of water to 1 mole of NaCl (total volume thus greater than 1 liter). However, the molality and molarity of dilute solutions are approximately equal. How would you make up 0.5 liters of 3M NaCl solution? Osmolarity is defined as the concentration of a solution expressed in terms of osmotically active particles, or osmoles (osmol/L or OsM). Osmotically active particles are any solutes that contribute to the concentration gradient. These can be either intact, uncharged molecules or charged ions. Physiological solutions are very dilute and are usually expressed in milliosmoles/L (mOsM). To convert between molarity and osmolarity, use the following equation: osmolarity (osmol/L) = Molarity (mol/L) x # of dissociated particles/molecule In the space below, show how would you make up 400 ml of a 200 mOsm NaCl solution?
Madhur L.
I have done my best to try answering the following questions correctly. I am unfortunately falling short on how confident I feel about how I am executing every answer. Step by step illustration would be very helpful. I simply want to feel confident in the step process, the mathematical part of these problems is what confuses me. 1. If 45.0 g of sugar is dissolved in 200.0 g of water, what is the mass percent of the sugar solution? I calculated 18.4 percent. 2. How many grams of a 23.4% salt solution are needed if you have 56 g of the salt in it? 3. How many moles of LiF would be present in 575 mL of 0.750 Molar LiF solution? I calculated 13.1 g. 4. What is the ion concentration of a solution prepared by diluting 10.0 mL of 6.0 HCl to a final volume of 200.0 mL? I calculated 0.3 M. 5. What are the final concentrations in a 0.15 M solution of MgCl2? I calculated 0.3 M. 6. What is the molality of a solution made by dissolving 35 g of NaNO3 into 2500 g of water? I calculated 0.16 mol/kg. 7. What is the change in freezing point given 1.6 moles of C6H12O6 into 4.3 kg of water? Kf for water is 1.86 C/mol. I calculated delta T = 0.69192. 8. What is the freezing point of a 2.2 molal Ca(NO3)2 solution? Kf for water is 1.86. 9. A 25.0 mL sample of 0.55 M HCl was titrated with 31 mL of Al(OH)3. What is the concentration of the Al(OH)3 given 3HCl + Al(OH)3 -> BaCl3 + 3H2? I can't recall the proper steps on how to even go about this problem.
Dinesh S.
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