DAT solutions general chemistry

When NaCl is added to distilled water, each of the following properties would increase EXCEPT one. Which one is the EXCEPTION? A. Vapor pressure B. Molarity C. Osmotic pressure D. Molality E. Boiling temperature

"Increase except" which one has the inverse relationship ↑boiling point, ↓vapor pressure A. Vapor pressure B. Molarity C. Osmotic pressure D. Molality E. Boiling temperature A. Vapor pressure

2.5gram sample of Lithium Chloride is dissolved in 53.5g of water. What is the percent by mass of Lithium chloride in this solution?

"Percent by mass" or 'weight by weight' formula is: mass of solute over mass of solution 1. add together masses given Mass of LiCl + mass of water = total solution mass (denominator ) Percent mass = grams of solute/ grams of solution

400 Liters of .6 M of sulfuric acid is required to react completely with .02 Liter sample of sodium hydroxide as shown. What is the molarity of the base?

"react completely"--> tells you will need a rxn ratio if the reaction is shown make sure its balanced 1.Balance the equation 2. Find moles of the acid 3. Use molar ratio of the acid and base to get moles for base 4. Plug it back into the Molarity formula which is moles of base / .02 Liters of base give.

How much water should be added to 10 mL of 3.00 M HCl(aq) in order to dilute it to a 2.00 M solution of HCl(aq)?

(3.00)(10) = (2.00)(V2) V2 = 15 mL 15 - 10 = 5 mL

Which of the following aqueous solutions has approximately the same boiling point as that of a 0.15 m NaCl solution? A. 0.10 m MgCl2 B. 0.20 m ethylene glycol C. 0.15 m glucose D. 0.15 m Na2S E. 0.20 m AlCl3

(m) * (i) = 0.15 * 2 ions = 30→ find the molecule that matches A. 0.10 m MgCl2

Which of the following solutions has a pH > 7 at 25 oC? NaCN (CH3)2NH NH4Cl

--Seperate into ions, we want the bases only bc ph >7 (negative charges) --Will the negative ion pull H+ charge I.CN- will pull II.N- will pull III. Cl- → will not pull bc it turns into HCl and dissociates --Ph >7 need basic solutions

10g of an unknown compound are added to water to form a 7.89 molar solution. If 2 liters of solution are present, what is the molar mass of the unknown compound? Test 3

-dimensional analysis; 10g always start with the easy units - (10g) (1L/ 7.89 mol) (1g assumed/ 2L) = --> 10g / 7.89mol * 2L -7.89 "molar solution" (M)--> (mol/L) ; 10 grams does not need to match we'll need it at the end You assume you need one mol to find the molar mass plug in 1 even though its not given 10 / (7.89) (2) molarity equation is M = Moles of solute / Liters of solution 7.89 = Moles of solute / 2(7.89)(2). The question asks for the molar mass which is defined as g/mol. Dividing would give you the unknown compound. MM = 10g / (7.89)(2)

volume increases as temp

-increases Thermal expansion concept

100 mM

-know mM is 1000 mM = 1M -set up dimensional analysis 100mM (1M/ .1000 mM)(39 g/ 1mol)

.02L of .05 M of Mg2+ in solution is desired. It is attempted to achieve this by adding .005ml of .005 M of MgCL2 and .015 L of Mg3(Po4)2. What is the concentration of Mg3(Po4)2

-we want a product --> final - initial always! Note the 3 in front of x because there are 3 potential Mg2+ generated from each Mg3(PO4)2 in aqueous solution. Solve for x: Mg3(PO4)2 + (MgCl2) = (Mg2+) Manipulate formula: (3X molarity)(.015 L) = (.05)(.02 L) - (.005M Mg2+)(.005 L) x = [(.05)(.02) - (.005)(.005)]/(0.045)

10 g of an unknown compound are added to water to form a 7.89 molar solution. If 2 liters of solution are present, what is the molar mass of the unknown compound?

0.63 g/mol

An aqueous solution of potassium chloride is heated from 20 Celcius to 60 Celcius (no vaporization occurred). Which of the following occurs while the solution is being heated? A. The mole fraction of solute decreases. B. The mole fraction of solvent increases. C. The density of the solution is constant. D. The molarity of the solution is constant. E. The molality of the solution is constant.

1. "aqueous solution" is the keyword think molality 2. molality is constant because it is not affected by temperature 3. molality is used when dealing with aqueous solutions -Molality is not affected by temperature!!!!! (this was repeated in the destroyer book) -Thermal expansion concept = volume increases as temp increases -Only factors that deal with volume will change, everything else stays constant E. The molality of the solution is constant.

100 mL of 0.50 M CaCl2(aq) is mixed with 100 mL of 0.25 M H2SO4(aq). What is the final concentration of [Ca2+] in this solution? CaSO4 is insoluble in solution.

1. MULTIPLY TERMS GIVEN: Find the number of mols of both ions that are insoluble (0.100 L)(0.50 M) = 0.050 mol Ca2+ (0.100 L)(0.25 M) = 0.025 mol SO42- (limiting) 2.SUBTRACT: You will have (.05 - .025 = .025) .025 CaCl left over to dissociate 3. PLUG INTO MOLARITY FORMULA (0.025 mol [Ca2+] leftover to dissociate ) / (0.200 L (total volume)) = 0.125 M [Ca2+].

At equilibrium, what is the concentration of Mn2+ in a solution that is buffered at pH = 12, if the Ksp = 1.6 × 10-13 for Mn(OH)2?

1. Separate into ions Mn(OH)2 → Mn2 + OH 2. Balance equation 3. Given Ph → 12-X=14= -2 thats concentration to OH (10^-2)

What is the molar solubility of BaF2 (Ksp = 1.8×10-7) in 0.10 M sodium FLUORIDE?

1. Write out ions of the molecule in question BaF2(s) Ba2+(aq) + 2F-(aq) (the equation tell you when theres an exponent) 2. 1.8 x 10-7 = Ksp = [Ba2+][F-]2 3. Ksp = 1.8×10-7 = (x)(0.10)2 4. x = 1.8 x 10^-7 / 1 x 10^-2 = 1.8 x 10^-5

At 25C a solution of NaBr has a density of 1.35g/ml. If this solutions is 15% by weight NaBr. What is the molarity?

1. by weight gives the ratio of 15 grams over 100 grams 2. density gives a ratio 1.35 grams/ml 3. conversion ratio to turn milliliters to liters 4. molar mass ratio for NaBr

What is the molar solubility of PbSO4 in 4.0 × 10-2 M Pb(NO3)2 solution? The Ksp for PbSO4 is 1.6 × 10-8

1.6 × 10-8 = 0.04x x = 4 × 10-7 = molar solubility

A compound contains 43% carbon, 16.7 Nitrogen and 2.5% Hydrogen. What is the empirical formula?

1.Divide percents by mass 2.Use smallest answer and divide all by that answer to give you subscripts of formula

An acid is 12M with a density of 1.7g/cm3. Calculate the percent mass of Acid in this aqueous solution. (molar mass of acid is 102g/mol)

1.Find grams of acid using given molar mass 2.Find grams of solution using density 3.Percent mass = mass of acid / mass of solution

1 mol of HNO3 is dissolved in 54.0 grams of H2O. What is the mole fraction of HNO3?

1.Find moles of H2o using grams given 54 (1mol/ 18g H2o) = 3mol 2. Add all mols: Mole Fraction formula is moles of HNO3 over 1 mol HNO3 plus 3 mols H2O = 0.25 Sometimes a question like this might be presented in a w/w (weight by weight) format.

A 29 Molar solution of and acid in water has a density of 1170g/ L. What is the mole fraction of this acid?

1.Use 29 Molar to find mass of acid (solute) 2.denominatior: Use density to find mass of total solution 3. Total solution grams - acid grams gives grams of solvent mole fraction = moles of solute/ moles of solvent similar to molality formula

How many mL of a 10 M acetic acid solution would be required to prepare 300 mL of a 2.5 M acetic acid solution? B3

70 grams This is a typical dilution problem.- MV = MV2

boiling point, vapor pressure, solvents

A certain fraction of the solvent molecules will have sufficient energy to escape from the surface (e.g., 1 in 1000 or 1 in a million). If you reduce solvent molecules on the surface, you are going to reduce the number which can escape in any given time. (reduced vapor pressure)

An aqueous solution of 0.75 M glucose has an osmotic pressure of 2.4 atm at 300 K. If the osmotic pressure is doubled, and the temperature were tripled, what would be the molarity of the resulting solution?

A. 0.50 M -You think you have to solve for osmotic pressure but just plug in the "changes" - ignore i and R of the formula plug in everything else The molarity will be 2/3 its previous amount. Solve for the molarity:

When a nonvolatiile hydrocarbon is dissolved in benzene, the partial pressure of benzene over the resulting solution

As more hydrocarbon moles are added the mole fraction of the solvent (benzene) decreases

400 Liters of .6 M of sulfuric acid is required to react completely with .02 Liter sample of sodium hydroxide as shown. What is the molarity of the base?

Balance the equation 1.Find moles of the acid; use L and Molarity given 2.Multiply moles of the acid with the molar ratio of the acid and base to get moles for base. 3.Plug it back into the Molarity formula which is moles of base over the .02 Liters of base give.

Which one of the following is the complete net ionic equation for the reaction of silver nitrate and sodium chloride?

Become Solids(stay in rxn) -grp 7n(halides) Cl,Br,F- and PO CO HO S- -Ca Sr Ba Pb Hg Ag Ag (here) precipitates here -eliminate spectator ions (non precipitates) AgNO3(aq) + NaCl(aq) → AgCl + NaNO3 Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) → AgCl(s) + Na+(aq) + NO3-(aq) Ag+(aq) + Cl-(aq) → AgCl(s Eliminate repeats (spectator)

Which of the following compounds is most soluble in CCl4? H2O BaSO4 CH3OH C8H16 NH3

C8H16 CCl4 is non polar everything else has a polar molecule

become solids

Cl,Br,F- with PO CO HO S- SO4- with Ca Sr Ba Pb Hg Ag https://www.youtube.com/watch?v=AsCLuLS-yZY

A researcher is analyzing two solutions. Solution A is found to have a higher vapor pressure than solution B. Based on this finding, which of the following conclusions can be made about solution A compared to solution B? A. Solution A has a higher boiling point and stronger intermolecular forces. B. Solution A has a higher boiling point and weaker intermolecular forces. C. Solution A has a lower boiling point and stronger intermolecular forces. D. Solution A has a lower boiling point and weaker intermolecular forces.

D. Solution A has a lower boiling point and weaker intermolecular forces. A has a lower boiling point and weaker intermolecular forces.

Given that Ksp of FeX2 is 5 x 10-6 where X is an uknown anion what is its solubility in moles er liter?

FeX2 → Fe2+ + 2X -bring the subscript up to be a power and it will be the coefficient as well Ksp = [2X]2

Which of the following solutions has the lowest freezing point? A. 0.20 m C6H12O6 B. 0.20 m Ba(NO3)2 C. 0.20 m H2SO4 D. 0.20 m Na3PO4 E. 0.20 m K2CrO4

For the ones that dissociate move the subscript to the front In C) you have 3 molecules D is answer

.4 * 300 = .15 *V V= 800 800ml - 300ml (initial) = 500ml

Hoe much water must be added to a solution to dilute .4M, 300 ml HCL to .15 M?

How much water must be added to a solution to dilute .4Moles, 300milliliters HCl to .15Moles?

How much water is basically asking for volume 1.moles multiplied by milliliters then divide by .15 moles to find your missing volume 2. Do not forget to subtract final found volume with the inital volume

Aqueous ammonium sulfide is added to a solution of iron (II) chloride. What are the spectator ions in this reaction? I. NH4+ II. S2- III. Cl- IV. Fe2+

I and III Write it out; NH4+ + S2- + Fe2+ + Cl- → FeS + NH4+ + Cl- NH4+ and Cl- appear on both sides They are spectator ions. -doesnt matter if its Fe with S, Sulfide will always precipitate SO4 and Grp 7 (Br, Cl, F) and "PO.CO HO.S- " (always precipitate) --Metal hydroxides (OH-) and oxides (O2-): Most are insoluble. --Salts of phosphates (PO43-), oxalates (C2O42-), chromates (CrO42-), and sulfides (S2-): Generally insoluble. Group 7 Br Cl F Sulfide will precipitate NH4 / Cl spectator ions bc they will stay soluble and free in the solution

A student dissolved 10.1 g of KNO3 (molecular mass of KNO3 = 101.10 g/mol) into 1000 mL of water. He then took 10 mL of the resulting solution and diluted it to 100 mL. What is the molarity of the second solution? A. 0.0010 M B. 0.010 M C. 1.0 M D. 1.0 × 10-4 M E. 1.0 × 10-6 M

In order to dilute you need the amount of initial mols ( use molecular mass to dimen. analysis) Dilute your initial molarity into each volume given (10.1 g) * (1 mol / 101.10 g ) = ___ mols Use mols to dilute into your different volumes A. 0.0010 M B. 0.010 M C. 1.0 M D. 1.0 × 10-4 M E. 1.0 × 10-6 M

Which best expresses the algebraic relationship between the molar solubility, x , of Ca3(PO4)2 and its solubility product constant Ksp?

Ksp = 108x^5

What is the molar solubility of barium fluoride in a solution that is 0.15 M NaF at 25o C. The solubility product constant for BaF2 at this temperature is 1.0 x 10-6.

Ksp = [Ba+2][F-1] 2 "2x" to be negligible compared to 0.15. substituting into the Ksp expression, we get 1.0 x 10-6 = (x) (0.15)2 solving for x, we get: x = 4.44 x 10-5 M

A solution has a density of 1280 g/L and contains 200 grams of Magnesium Nitrate. What is the molality?

Molality formula: grams of solute / kilograms of solvent 1.Find moles of solute (magnesium nitrate) by using grams given 2.Find grams of total solution using density given --> Molality formula is different than percent mass dont confuse them --> Molality is solute/ solvent vs. percent mass is solute / total solution --> Molality uses solvent in denominator vs. percent mass uses total solution 3.Subtract solution total minus solute to get the solvent

A 29 Molar solution of and acid in water has a density of 1170g/ L. What is the mole fraction of this acid? (the acid has a molecular mass of 20g/mole)

Mole fraction formula is moles of acid over total moles

A 2.5gram sample of Lithium Chloride is dissolved in 53.5g of water. What is the percent by mass of Lithium chloride in this solution?

Percent by mass or weight by weight formula is mass of solute over mass of solution

50 grams of glucose (c6h12o6) and 50 grams of sucrose (c12h22O11) were each added to beakers of water which of the following would be true?

Since glucose has a smaller molecular mass than sucrose, there will be a greater number of moles of glucose present when equal masses of the two substances are used. glucose mole fraction= small/ total= large number sucrose mole fraction= large / total= small number what is the answer to this??

The boiling point of a 1.0m aqueous solution is 101.5°C. The molal boiling point constant for water is 0.512°C•m-1. Which of the following substances is most likely dissolved in the water?

Solve for i ("dissolved" is key word) Boiling point = 101.5 given minus water boiling point 100

The vapor pressure of pure liquid X is 400mmHg and the vapor pressure of pure liquid Y is 200 mmHg. Based on this information, which of the following findings would the chemist likely observe?

The vapor pressure of pure liquid X is greater at 400mmHg than that of pure liquid Y. The solution of X and Y will have more molecules of gas X .

An aqueous solution of potassium chloride is heated from 20C to 60C (no vaporization occurred). Which of the following occurs while the solution is being heated? A. The mole fraction of solute decreases. B. The mole fraction of solvent increases. C. The density of the solution is constant. D. The molarity of the solution is constant. E. The molality of the solution is constant.

Thermal expansion concept = volume increases as temp increases Only factors that deal with volume will change, everything else stays constant Molality is not affected by temperature!!!!! (this was repeated in the destroyer book) E. The molality of the solution is constant.

You always jump to just plugging it in Remember the formula asks for mols/ L Use the grams to find mols

What is the overall molarity of a solution prepared with 60g of calcium bromide in 500 ml solution?

A small amount of aqueous NH3 is added to a solution of Cu2+ and a precipitate forms. However, when excess aqueous NH3 is added, the former precipitate dissolves. Which statement best explains why the precipitate dissolves with excess aqueous NH3?

When excess of NH3 is added the h20 is outranked by EXCESS NH3 (now becomes the dilute)

"like dissolves like" principle. Because CCl4 is a nonpolar molecule other nonpolar substances will be most soluble in CCl4. C and H are considered non metals and are covalent H2O BaSO4 CH3OH C8H16 NH3

Which of the following compounds is most soluble in CCl4?

density

a good way to get molar mass of a solution

Which of the following weak acids ionizes to give the strongest conjugate base?

a) HClO (b) CH3COOH (c) HF (d) HNO2 (e) HCN answer: e all of them have O's high electronegativity --> N is the least electronegative (making the weakest acid) --> (strongest base)

What is the mass percent of methanol in a solution prepared by diluting 16 grams of methanol with 32 grams of water?

add for total grams of solution; plug into division equation -mass percent = grams solute/ grams solutionmass --percent = 16 / 16 + 32 = 16/48 = 33% 33 %

Sulfuric acid is stored in a protective container to prevent it from corroding the container. If 250mL of the 4.5M stock solution of sulfuric acid is to be transferred to an empty flask, what volume of water in liters must be added to the flask to reduce the sulfuric acid's molarity to 2.2M?

added --> means subtract (final - initial)

at 25C osmotic pressure of blood is about 7.7 atm. What concentration of KCl is isotonic with blood. assumind the potassium chlorid dissociates? .32 .16 6.4 3.2

answer: 0.16 pressure = iMRT (manipulate to solve for M) bc "what is the concentration"

Arrange the following salt solutions from lowest to highest pH. NaBr KF NH4I

basic = high PH strong base and a weak acid, the pH of a solution will be > 7, i.e. basic. It if is a salt of a strong acid and a weak base, the pH of a solution will be < 7, .e. acidic. If it is a salt of a strong acid and a strong base, the pH of a solution will be 7, i.e. neutral.

What is the boiling point of a solution of 5.0 mol of glucose dissolved in 1000 mL water? (Kb for water = 0.512oC / m; assume density of water = 1g/mL)

boiling point!!! T= (i)mKb Glucose does not dissolve i=1 REMEMBER: Add Tb to boiling temp of 100 degrees to get final answer 102.6

boiling point and vapor pressure

boling point is when vapor pressure of the liquid = ambient pressure as solutes are added to a solution the vapor pressure will decrease

5g of NaOH is dissolved in 200ml of H2O. Find Molarity

dont over think it 1.find mols! 2.use grams to find mols Molarity is mols over liters (plug in to formula) 3.set up found mols over liters of H2O

A solution of NaBr has a density of 1.35. If this solution is 15% by weight NaBr. What is the Molarity?

formula: (w/w) (density)(molar mass)= molarity 1. by weight gives the ratio of 15 grams over 100 grams 2. use density ratio (1.35 g/ 1 ml) 3. find molar mass use pd. table (Xgrams/ 1 mol)

By weight meaning

grams of given solute over 100 grams of solution

An aqueous solution of 0.75 M glucose has an osmotic pressure of 2.4 atm at 300 K. If the osmotic pressure is doubled, and the temperature were tripled, what would be the molarity of the resulting solution?

i.osmotic presure (pi)= miRT ii.2pi=miR3Tm=2/3 iii. 2/3 * the original molarity iv. 2/3*0.75 -You think you have to solve for osmotic pressure but just plug in the "changes" - ignore i and R of the formula plug in everything else -The molarity will be 2/3 its previous amount. Solve for the molarity:

Which of the following solutions has the lowest freezing point?

lowest freezing point The one with MORE/HIGHER (i) will affect MORE the freezing point formula

mass percent vs. mol fraction

mol fraction uses mols and can be used to find grams ->(mass percent)

What mass of CCl4 (in grams) is needed to dissolve 16 g of Br2 to make a 0.5 m solution of Br2?

molality= moles of solute/ kg of solvent 1. find mols (GRAMS + MW)-->16 g of Br2/ 160 g/mol of Br2= 0.1 moles of Br2 2. find kg by manipulating the moLality formula --> 0.5m = 0.1 mols of Br2/ X kg of solvent --> x kg of solvent= 0.1 moles Br2/ 0.5m = 0.2kg -->0.2kg/ (1000g/ 1kg)= 2 x 10^ 2 g

finding molarity using w/w solution and density

molarity = (ww%) * (density) * (molar mass) (mol/grams)

What is the concentration in molarity of a 25% (w/w) solution of HClO4 (MM = 100.46 g/mol) that has a density of 1.5 g/mL? A. 1.50 M B. 3.75 M C. 25.0 M D. 40.0 M E. 66.6 M

molarity = ww% x density x molar mass write the ratios out (25/100) (1.5g/ .001L) (1 mole/ 100 g Hclo4)

molality

multiiply: they give you grams but you need to find MW!! dont jump the gun!!!! find mols--> mols for mol. lality

An acid is 12M with a density of 1.7g/cm3. Calculate the percent mass of Acid in this aqueous solution. (molar mass of acid is 102g/mol)

percent mass formula is : mass of solute or acid ------------------------ mass of solution. 1. MULTIPLY GIVENS:Find grams of solute using (M) given and given molar mass --> (12 moles)(102 g/mol) 2.using density: Find grams of solution (easy just convert to liters) 3. percent mass = mass solute (step 1)/mass solution(step2)

Sulfuric Acid DISSOCIATION (H2SO4)

separates into 1 mole of negatively charged sulfate ions, or SO4(2-), and 2 moles of positively charged hydronium ions, or H3O+. total of 3 moles

A solution that contains more of the dissolved material than could typically be dissolved by the solvent is defined as:

supersaturated solution "more than typically can be" = super

Which of the following expressions correctly gives the pH of a 1.0 M solution of NH3 (Kb = 1.8 x 10-5)?

takes an extra step to find pH

What volume of water would be needed to dilute 50 ml of 3M HCL solution to 1M?

the amount we needed (final- initial volumes) -M1v1 = m2v2

Group 7 Br Cl F

will precipitate with SO PO CO HO S- (sulfide)

What is the molecular formula of a compound composed of 24% carbon and 76% fluorine, given that its molecular weight is 200g/mol

you are given the percents of the total --> multiply the total and the percent to get the MW grams of each .76/200--> x grams FIND GRAMS: .24/200--> x grams xgrams/ MW of atom( grams/mol ) --> mols 1 xgrams/ MW of atom( grams/mol )--> mols 2

Which of the following values is needed to calculate boiling point elevation?

ΔT = i (Kb)(m) molality