Phy chem 2

What is the most efficient way to perform an extraction to maximize the amount of solute extracted ?
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as molar mass increases, solubility in water tends to decrease
- more polar groups in the molecule = more water soluble
- more nonpolar groups in the molecule = more nonpolar and more likely to cross the blood-brain barrier
- low molar mass and more polar functional groups = more water soluble --> if it has functional groups that are water soluble, even more water soluble
- THC (found in marijuana) is fat-soluble: why THC can be found in the body via a urine test weeks after smoking marijuana
After extracting with ethyl acetate, a student drained the aqueous layer from the separatory funnel, then rinsed the funnel with 5 mL of ethyl acetate and added it to the organic phase before evaporating the solvent. Her lab partner told her that the additional 5 mL of ethyl acetate would lead to an error in the calculation of Kd. Is this correct?
What defines acidic, basic, and neutral solutions in terms of the absolute and relative {H3O+} and {HO-} and pH?Neutral: ph=7 / {H3O+}= 1 * 10 ^-7 M / {OH-} = 1 * 10 ^-7 M Acidic: ph <7 / {H3O+}> 1 * 10 ^-7 M / {OH-} < 1 * 10 ^-7 M Basic: ph>7 / {H3O+}< 1 * 10 ^-7 M / {OH-} > 1 * 10 ^-7 MWhat is the relationship between conjugate acid-base pairs ?Strong acid= weak base, and strong base = weak acidWhich of the methods used in the lab was the most precise for determining pH? Which was the least precise?The ph meter was the most precise while the color indicators were the least precise.What characterizes a weak acid in terms of its pka, the ph of its solutions relative to strong acids and their ability to dissolve in waterWeak acids have a higher pka value and higher ph, only partially dissociate, leaving fewer ions in solution. Stronger acids have a lower pka value and lower ph value, strong acids have a large dissociation constant, so they dissociate completely in waterHow do solutions of strong and weak acids of the same concentration differ in their ph? For example, if you have 0.001 M HNO3 and 0.001 M CH3CO2H, do you expect the measured ph to be the same.HNO# is a strong acid so the ph reading will be lower while CH3CO2H is a weaker acid so the ph reading will be higher.How is a titration defined and what is its underlying chemical principles ?Is a procedure in which acid base neutralization reaction is used to determine unknown concentration.What is a back titration and what is its underlying principles ?titration in which a precisely known excess of titrant is added to the analyte solution and the amount of titrant added in the excess becomes the new analyte which is then titrated with a second standard titrant. It is useful if the end point of the reverse titration is easier to identify than the end point of the normal titration.How does one read a buret and how many decimal places does it provide?Read initial liquid level to the nearest 0.01 of an mL by looking at bottom of meniscus.What makes a substance an amphillic/amphipathic versus amphiprotic/amphoteric ?amphillic/amphipathic has a hydrophilic ("water-loving") or polar end and a hydrophobic ("water-fearing") or nonpolar end•ex. soap/detergent. amphiprotic/amphoteric can behave as acid or base depending on reacting partner•ex. water & PROTEINWhat is the utility of a chemical indicator in an acid-base titration ?To determine the end point of the titration which is when neutralization has occurredWhat is the primary standard and what are its characteristics ?KHP is an example and it is a highly stable substance obtainable with high purity after being thoroughly dried and that allows for the precise and reproducible determination of the unknown concentration of a solute in a solution.What is the effect on the standardization of a basic solution with KHP of... losing a small amount of KHP when transferring it to the collection Erlenmeyer flask after weighing?moles of KHP / volume of NaOH = M of NaOH -↓KHP ↓NaOH -OVERESTIMATE concentration → M of NaOH ↑What is the effect on the standardization of a basic solution with KHP of... adding a small amount of water to the solid KHP to fully dissolve it before adding the base?•moles of KHP / volume of NaOH = M of NaOH-does NOT affect if because it has to do with acid and baseWhat is the effect on the standardization of a basic solution with KHP of... rinsing the tip of the buret with a wash bottle while dispensing base before the end point and allowing that rinseto enter the collection flaskmoles of KHP / volume of NaOH = M of NaOH-does NOT affect because water has NOTHING to do with acid & baseWhat is the effect on the standardization of a basic solution with KHP of... mistakenly adding a few extra drops of base into the Erlenmeyer flask when approaching the end point and having the phenolphthalein turn bright pink (overshooting)?moles of KHP / volume of NaOH = M of NaOH-↑NaOH-UNDERESTIMATE concentration → M of NaOH ↓What is the affect of adding a small amount of water to the antacid solution before adding standardized NaOH solution ?It causes the tablet to dissolve because of a chemical reaction.By what factor does the acidity of a solution change for every unit change in pH?A change of one pH unit changes the hydrogen ion concentration by a factor of tenWhat are the physiological functions of hydrochloric acid in the stomach?Initiate the conversion of pepsinogen, the inactive precursor of pepsin, to the active enzyme pepsin → once pepsin is formed, it acts on other molecules of pepsinogen to form more pepsin, as well as on dietary proteins •denature proteins (i.e., unfold coiled protein chains) in order to more efficiently promote their degradation by enzymes •provide the necessary pH in which the enzyme pepsin can break down protein molecules with optimum efficiency•pH on empty stomach = 1.0•pH when full = 3.0What is a buffer?Will maintain near constant ph when challenged with small amount of acid or base.How to make ph of base go down if too high to be acidic ?Add buffer to a little acid ph will drop.What is a neutralization reaction and what does it produce in aqueous solution ?A neutralization reaction is a reaction in which an acid and a base react in an aqueous solution to produce a salt and waterHow is pH calculated from [H₃O⁺] and vice versa?•pH = -log[H₃O⁺] •[H₃O⁺] = 10⁻ᵖᴴHow does one identify a Lewis acid or base in a chemical reaction?lewis acid: any substance capable of accepting a pair of electrons via the formation of a coordinate covalent bond •lewis base: species that donates the pair of electrons to bond the lewis acid •ALL bronsted-lowry acids are also lewis acids, but the converse is NOT true•bronsted-lowry bases are also lewis bases and vice versaHow are buffers prepared and what are their functional characteristicsa buffer is a solution that can resist changes in pH due to the presence of chemical species that can neutralize both acidic and basic compounds, typically a mixture of a weak acid and its conjugate base •for optimal buffer capacity, when making a buffer of particular pH, the acid of choice should have a pKa that falls within one pH unit of the desired pH •ratio of conjugate base to acid fluctuates between 10 - 0.1 •ex. weak acid (acetic acid) mixed with conjugate base (sodium acetate)What are common physiological buffering species in blood and how do they neutralize acids and bases ?The lungs influence the reaction by controlling the amount of Co2 in the body while the kidneys influence it by independently controlling the amount of bicarbonate in the blood. The reaction of CO2 with water produces both acid and the basic bicarbonate anion, determines acid base balance within the body.Why do hydrogen peroxide solutions last longer when stored in brown bottles in the refrigerator ad why should you keep it away from face when opening ?stored in brown bottle to prevent light from affecting the solution because when left in warm temperatures it can cause it to breakdown into H2O AND O2 .-Light enhances its rate of decomposition -Keep face away because sealed cap creates a pressured environmentWhat are the various energy changes that take place when an ionic solid dissolves in water and how does the net energy change of the dissolution process relate to the final temperature of the solution?Exothermic releases energy. temperature increases Endothermic reaction absorbs energy. temperature decreasesWhat happens when a substance is oxidized? What about when it's reduced? How can one tell whether an oxidation or reduction has taken place in a reaction involving organic compounds?The atoms that lost electrons are said to be oxidized. Reduction is the gain of electrons If the oxidation state is becoming more negative, it's a reduction (gaining electrons). If the oxidation state is becoming more positive, it's an oxidation (losing electrons).