CHEM1003 Lecture Notes - Lecture 17: Volumetric Flask, Erlenmeyer Flask, Sodium Chloride

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11 Jul 2018

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A concentration states the amount of solute in a given solvent. Quantitative: molarity, percentage conc, parts per million. Conc is how much of something in a given amount of something. Defined as the number of moles of solute dissolved in 1 litre of solution. C for concentration, n for number of moles (mol), v for volume in litres. The units are moles per litre (mol l^-1 or m) A student prepared a solution of nacl by dissolving 1. 461 grams of nacl in a 250 ml volumetric flask to study the effect of dissolved salt on the rusting of an iron sample. 1st step= calculate how many moles in 1. 461 grams of nacl: 1 mole of nacl is 23 +35. 5= 58. 5 grams mol^-1 so 1. 461 grams= 1. 461g/58. 5g mol^-1= 0. 02 moles. 2nd step= dissolving 1. 461g (0. 02 moles) of nacl in a 250ml volumetric flask the conc of this solution c= n/v c= 0. 02/0. 250= 0. 8 mol l^-1.

Related Questions

7. Complete the following table:

Element Moles Mass Num

7. Complete the following table:

Element Moles Mass Number of molecules

13. It is the component that is in a solution, in smaller quantity.

a. Solution

b. Solvent

c. Solvent

d. Soluto

14. It is the component that is in a solution in greater quantity.

a. Solution

b. Solvent

c. Solvent

d. The answers b and c are correct.

15. The quantitative expression of the dissolved amount of solute in a quantity determined solvent is known as:

a. Solution

b. Volume

c. Concentration

d. Stoichiometry

16.Express the moles of solute among the liters of solution

a. Molality

b. Molarity

c. % weight by volume

d. % weight by weight

17.Express the moles of solute between kg of solvent

a. Molarity

b. ppm

c. ppt

d. Molality

18. What is the molarity of a solution prepared by dissolving 7.50 g of nitrate of magnesium, Mg (NO3) 2 in enough water to prepare 25.0 mL of solution?

a. 10.3 M

b. 5.6 M

c. 6.5 M

d. 2.03 M

19. How many grams of sodium chloride, NaCl are needed to prepare 125 mL of 0.037 M NaCl solution

a. 1.021 M

b. 0.268 M

c. 0.201 M

d. 0.500 M

20. Calculate the molality of a solution containing 12.5 g of ethylene glycol (C2H6O2) dissolved in 135 g of water.

21. A solution of ethylene glycol contains 21.2 g of ethylene glycol (C2H6O2) in 85.4 mL of water. Calculate the freezing point and the boiling point of the solution. (Assume the water density is 1.00 g / mL)

22. At what volume should you dilute 75 mL of a 10.0 M solution of H2SO4 to obtain a 1.75 M solution of H2SO4.

Experiment 10 Colligative Properties Introduction A pinch of wa make boiling water hotter. A handful will clear the snow from your steps. Every day we the physical properties of materials around us, but often don't know why we use these particular s or what chemistry is involved. Modifying the temperature of phase changes, by adding a second chemical to the pure solvent are examples of manipulating the Colligative Properties of a solution. this lab, we will study how varying the concentration and type of a salt affects the point of a solution. Colligative properties are properties of a solution containing 2 or more components. Typically, the primary is the solvent and the other called the such as color or hardness, properties depend on the number of particles of astute in the not the identity of the In many cases, the rokute will determine the number of solute particles (degree of ionization, solubility, etc,) in the solvent, but a colligative property does not depend upon the nature of the particles. Two colligative properties commonly encountered are boiling point elevation and freezing point depression (the temperature of of a is lower than of pure solvent). We will be studying boiling point elevation in this Most of the previous work that you have done with solutions has involved units of molarity, M, or moles of solute per liter of solution. Boiling point elevation calculations (as well as those for freezing point depression) or moles of solute per kilogram of solvent. boili change of temperature. When the temperature of a solution changes, the volume of the solution also changes. Since molarity depends on a change in wil the solution's molarity. Molality depends on the mass of the solvent. and thus is independent of temperature. n't Hoff Factor salt into and the of moles inorganic salts in an aque the based on the addition of the number dissociates, the total number of particles in the solution will be of cations and anions produced from the dissociation. Thus; Nacion Na Choaa (2moles of particles) Cacbrs Ca +2ch (3moles of particles) The quantity of particles produced per mole of solute is called the van'tHoff factor and is given the symbol, i, If 1 mole of sodium chloride were completely dissociated, iwould be 2. This theory works very well for dilute solutions and non-electrolytes (i 1, no dissociation at all since nonelectrolytes not ionize), For does not always apply to more concentrated solutions. Thus, when there are a large number of particles in a solution, they have a tendency to recombine as the salt and you don't get 100% dissociation. example, at a NaCl concentration of 0.1M, iwill be 1.81 (90% dissociation) rather than 2 (100%). Boiling Point Elevation solute causes the solution to boil at a higher When a solution is heated, the presence of a non-volatile point of the pure liquid and the temperature than the pure The difference between the boiling boiling point of the solution is: 169

Activity accounts for electrostatic interactions. For well-separated ions, electrostatic interactions are minimal; ions behave as at infinite dilution. As concentrations increase, distance between ions decreases and electrostatic interactions of force and energy increase. Consider the distance d between ions in solution. A spreadsheet is advisable. Find the equation for the distance between two ions in solution when the ions are present at a concentration c (mol/cm^3). In a spreadsheet, for log c from -12 to -2, calculate c and d. Increments of 0.5 in log c are appropriate. Units are c in mol/cm^3 and d in cm. Include calculation of concentration in molar units and separation distance in nm. What is the volume of one water molecule? What is the diameter of one water molecule in nm? Consider number of water molecules between ions as a rough estimate of the strength of electrostatic interactions between the ions. In the spreadsheet, how many water molecules are between two adjacent charges as a function of concentration? Plot log #waters versus log c(M). At what concentration is there about one water molecule between two ions? Comment on the shielding between two ions as concentration increases. In addition to shielding ions, water can be bound to ions. Once water is bound to ions, it is no longer free and therefore no longer part of the solvent. This increases the effective concentration of the ions because the solvent volume and mass has decreased. This is the Stokes Robinson model for activity, which is not explored in detail here. But, consider how bound water increases with c. (Part d is based in volumes, not distance between ions.) For a monocation, such as Na^+, the number of bound waters changes with ion size. For purposes of discussion, allow 5 bound waters per monocation. Anions such as Cl^- hold fewer waters; estimate this as 1. Then for every NaCl dissolved in solution, 6 waters are bound. To the spreadsheet, calculate the moles of each NaCl and water in cm^3. This calculates total moles of water per cm^3. Calculate the moles of free water at each concentration, which is total moles of water/cm^3 - 6 times moles NaCl/cm^3. Plot total moles of water, moles of free water, and moles of bound water per cc versus log c(M). At about what molarity of NaCl does the bound water begin to impact the free water? How does this correlate with the upper limit for Extended Debye Huckel (EDH)? Does EDH account for free and bound water? Density is 1.00 g/cm^3. Calculate volume of free water per cm^3. At what NaCl concentration does the model fail? How do you know? Calculate the effective concentration of NaCl as the moles of NaCl per cm^3 per volume of free water per cm^3. Calculate ratio of effective to real concentration of NaCl. What is c(M) where there is a ~2% change? a 20% change? a > 100% change? At about what concentration does free versus bound water become important? Calculate the mole fraction of NaCl (moles NaCl/(moles NaCl + total moles H_2O)) at each c. Report mole fraction in ppm. What mole fraction (ppm) corresponds to ~2%, a 20%, and > 100% change found in the just previous question? Fill in the blank or select an answer as appropriate. At ~ M, activity is not well modeled by extended Debye Huckel (EDH) as EDH does not account for free and bound waters. As concentration of ions increases, activity effects are more/less pronounced.

CHEM1003 Lecture Notes - Lecture 17: Volumetric Flask, Erlenmeyer Flask, Sodium Chloride

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