CHEM 112 Study Guide - Final Guide: Supersaturation, Molality, Mole Fraction

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redant354

21 Mar 2019

School

UMASS-Amherst

Department

Chemistry

Course

CHEM 112

Professor

Prof. Scott M. Auerbach

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Document Summary

Miscible and immiscible these terms are customarily appliedonly to solutions of liquids in liquids if two liquids dissolve in each other in all proportions they are said to be miscible. If twoliquidsare insoluble in each otherthey are said to be immiscible liquidsthatwill dissolve in eachother in appreciable but limited amounts are said to be partically miscible. Solute water finding how much water to add. 1 calculate moles that will be used fromgrams grams of y given x 1m mot y molarmass y. 2 calculate the mass of waterneeded from the molarity. X 1000g kg y g g finding how much of x compound to add. 1 calculate moles of x from the molarity mot x mot of given mo x k. 2 calculate the mass of x g x mot x x molarmassoft mo 1 x g x finding molarity. 1 calculate the moles of a mo l a g of a given xlmola_ molar massa not a.

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I can't seem to figure this one out. thank you!

BAEDitemViewlassignmentProblemiD-830644918offset next 121C1 12 Introduction to Solutility and Solution Formation troduction to Solubility and Solution Formation arning Goal understand the solubility of a solute in a solvent, the dissoltion p peocess, and the properties that afect the rate of dissoluÅ¡on ocess, and the properties that affed the rate of cola has a certain amount of carbon dioxide dissolved in t The cola is theretore olecular level, the dissolution process involves breaking intermolecular forces of aty action rious parameters, such as temperature, pressure, the nature of the solute, and the r example an incresse in temperature may increase the rate of dissoludon for solutions hwolving solds an example of a solution of gas in waler. The carbon daxide gas is the solute and it is diessved in water,which is nature of the solvent One can increase or decrease the solubility of solute by changing hese parameters e f the solvere At the among the solute molecules and forming new ones with the solvent moleciles The solublty af a solute in a salent depend art A The properties of a solute and its solubility in liquid solvents A solution is a homogenous mixture of solute and solvent There are diHarent types of soluions. A carbonated drink ia an example of a solution where the solute is a gas and ths saveet is a iquid Sugar crystas a in water is an example of a solution where the solute is a solid and the solvent is liquid Aceic acid is miscible in water, forming a solution commonly known as vinegar ln this case both the solure and the sohen iquids The solubility of solute in a solvent depends on various parsmeters, such as temperature pressura, tha nature of the solute, and the nature of the salvent Considaring thesa paranters iderdfy the ts correct for the solublity of a solute in a solvent Check all that apply Hints Table salt dissolves in water to form a solution Zinc sullate is soluble in water Gases are readly soluble in water t higher tamperatures Carbon dioxide gas will be more soluble in water when the partial pressure is high Propanol and heptane are miacible Dei My Awers Give Up

Question about mixed solvents for recrystallization.

I am having a hard time conceptualizing how a mixed solvent would work in a scenario where P and O nitronitroacetanilide are recrystallized with a small amount of hot Ethanol followed by a larger volume of water.

From the structure of the molecules I assumed that the Para form of nitroacetanilide is more polar than the Ortho form. Second, I know that water>ethanol for polarity. Finally, I know that water and ethanol can hydrogen bond with one-another and with itself. Also I know that water and ethanol will hydrogen bond together to form a more densely packed liquid. I imagine that this would look somewhat like this: [ Eth-OH] --[O-H2]---[OH-Eth]

My understanding of dissolving is that the solute gets surrounded by solvent molecules and separates from other solute molecules. This happens to all the solute molecules until no more solvent molecules are left to dissolve the solute.

Having said that, does the following make sense? If not, please correct me

1) the O/P mixture of crude nitroacetanilide dissolves in hot ethanol because ethanol hydrogen bonds with the nitroacetanilide

2) when water is added, ethanol and water hydrogen bond with one another creating a denser solvent because the ethanol hydrogens are attracted to the oxygen in water and vice versa

3) because there's less hydrogens "available" to form new hydrogen bonds after the water is added, the solvent can't make new hydrogen bonds as easily

4) because the P-nitroacetanilide needs more hydrogens to dissolve due to it being more polar, it is now less soluble in the ethanol/water mixture. this causes it to precipitate out while leaving the O-nitroacetanilide that's less polar still in solution

Is this correct? if not please explain how the mixed solvent helps precipitate the p-nitroacetanilide but maintain the o-nitroacetanilide in solution.

CHEM 112 Study Guide - Final Guide: Supersaturation, Molality, Mole Fraction

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