Saturday
October 25, 2014

Posts by chem


Total # Posts: 109

Ochem
What volume of eugenol will be present in 30 mL of distillate? The essential oil found in cloves, eugenol, can be isolated by steam distillation because it is insoluble in water and has a measurable vapor pressure at 100 °C even though it has a much higher boiling point ...
August 4, 2014

Chemistry
carbon dioxide dissolves in water to form carbonic acid. Estimate the thermodynamic equilibrium constanst (K) for this reaction (delta Gf values: H2CO3= - 616.1, H2O= - 237.1, CO2= - 394.4) . Carbonic acid then ionizes in water (Ka1= 4.5 x 10^-7). Ignoring Ka2, estimate (K) ...
March 21, 2014

CHEM
A particular reactant decomposes with a half-life of 139 seconds when its initial concentration is 0.342 M. The same reactant decomposes with a half-life of 237 seconds when its initial concentration is 0.201. What is the value and unit for this rate constant?
January 25, 2014

Chem
4.30 grams of NH4Cl is added to 14.5 grams of water. Calculate the molality of the solution
January 20, 2014

Chemistry
When weighing liquid ethanol, why do you have to place water in the beaker prior to adding the ethanol to that same beaker?
November 24, 2013

chemistry
Which of the following statements describes why ion exchange of 99% SiO2 - 1% B2O3 in a salt bath of molten postassium chloride (KCl) is not an effective way to increase the surface strength of the glass sample? The ion exchange works correctly, however both air-cooling and ...
November 1, 2013

science
C6H12 = 6x12 + 6x1 = 78. The equation indicates that 2x78 = 156g benzene will produce 6542kJ. Using proportions you can then calculate that x/6542kJ = 8.1g / 156g x = 339.7kJ = 339700J. heat = mass x ΔT x 4.18J/g° ΔT = 339700J / (5691g x 4.18J/g°) = 14.3°...
October 17, 2013

chemistry
11.76
August 29, 2013

Chemistry
What is the pH of a 0.20 M HF solution that is 5.8% ionized at 25 Celsius ? A.4.45 b.0.70 C.1.93 D.1.23 E.1.40
March 19, 2013

Chemistry
What are answers of a) and b) ??
January 11, 2013

Chemistry
Image one (d) Image two (a) I hope this helps. :)
November 22, 2012

Stela
CCl4 ClO4− ClF4− SiCl4 SO42− Which molecule or ion does not have a tetrahedral molecular geometry?
October 25, 2012

Chemistry
Btw, I did it the way you said and I still come up with the same conversion of 29.8 * (760/1)= 22648
October 25, 2012

Chemistry
Sorry, my post repeated by accident when i refresh my page
October 25, 2012

Chemistry
Using the "octet rule" write the Lewis formulas for NF3 and NO3-.
February 22, 2012

Chemistry
How do you draw a lewis dot structure of s3o
February 22, 2012

chem
How to find the %(W/V) of 134mL of a 0.610 M solution of Mg(OH)2
February 16, 2012

Chemistry
Explain the function of the aluminum wire and the mercury II chloride when testing for tin? when testing for antimony, what reagent prevents tin from reacting with the H2S to form SnS2? What reagent is used to identify copper and explain its function.
October 16, 2011

chemistry
How much energy (in kilojoules) is released when 21.0 of ethanol vapor at 94.5 is cooled to -19.0?
September 12, 2011

organic chem
cadaverine is AKA pentane-1,5-diamine
April 26, 2011

Chemistry
In the laboratory exercise "Preperation and Properties of Polymers", polyvinyl alcohol is dissolved in water and then reacted with borax (Na2B4O7·10H2O) in water. Which of the following are expected results of this reaction? True or False? 1. Polyvinyl alcohol...
April 22, 2011

Organic Chemistry
Suggest structures for C10H14O; C10H16; C10H18; C10H16O3; C10H16O2 ; C12H22O2 in the following reaction schema: The UV/Visible spectrum for C10H14O exhibits a at 244 nm C10H16 + hot KMnO4 + H2SO4 → C10H16O3 C10H16O3 + Zn(Hg)/conc HCl → C10H18O2 C10H18O2 + CH3CH2OH...
April 6, 2011

Organic Chemistry
The UV/Visible spectrum for C10H14O exhibits a at 244 nm C10H16 + hot KMnO4 + H2SO4 → C10H16O3 C10H16O3 + Zn(Hg)/conc HCl → C10H18O2 C10H18O2 + CH3CH2OH + H3O+ → C10H22O2
April 6, 2011

chem
Sarah, 4.70 is what you get when you do the -log (Ka)
April 4, 2011

chem
Thank you
April 4, 2011

chem
Calculate the volume of 0.200 M acetic acid and the volume of 0.100 M sodium acetate required to make 200.0 mL of a buffer solution with pH = 5.00. The Ka for acetic acid at 298 K is 2.00 x 10-5.
April 4, 2011

chemistry
I don't understand how you do (b), I got 173kJ for (a) and I understand Hess's law for (c), but (b) I really don't understand (b)
March 30, 2011

Chemistry
True/False 1. Diatomic molecules contain two atoms?T 2. Electrons travel in pairs? T 3. The energies needed to break chemical bonds can be measured T 4. Bonding involves all the electrons in an atom T 5. Lewis structures are used to describe bonding? F 6. More than one pair of...
January 16, 2011

science
An excess of aluminum metal is added to 200.0 mL of 0.025 M solution of CuCl2, reducing the Cu+2 ions to metallic Cu. If the temperature of the solution increases from 25.0 to 27.5 degrees celsius, what is the enthalpy of this reaction per mole of Cu formed? (Specific heat of ...
December 29, 2010

chemistry equilibriums
At a certain temperature, 2.00 moles of phosphorus(V) chloride, PCl5, was placed in a 1.0 L vessel and permitted to react as shown: PCl5 (g) <-> PCl3 (g) + Cl2(g) At equilibrium, the container held 0.40 PCl5. What is the numerical value of Kc for the system as written? A...
December 29, 2010

chemistry
C3H7OH right?
December 28, 2010

chemistry
On complete oxidation, one mole of an organic compound produced four moles of water. Which one of the following substances could it be? CH4 C2H6 C3H7OH C4H10 So I added O2 to each of these compounds, but I must be doing something wrong because I can't get 4 moles of water...
December 28, 2010

Chemistry
ln166.44-lnx=0.64766*1.73 -lnx=1.120-ln166.44 lnx=3.9942 x=E^3.9942 =54.27 166.54-54.27=112g
December 25, 2010

Chemistry
Sucrose hydrolyzes into glucose and fructose. The hydrolysis is a first order reaction. the half life for the hydrolysis of sucrose is 64.2min at 25C. How many grams fo sucrose in 1.25L of a 0.389M solution are hydrolyzed in 1.73hrs? I started off by finding k the constant t1/...
December 25, 2010

Chemistry
Thank you for you help
December 25, 2010

chem: study of kinetics
he gave us an example of what the slope might be in class and it was -1.3x10^2 but my slop is completely different, was i supposed to do calculations? or just get the one from excel? what do i put in the 2 blanks?
October 16, 2010

chem: study of kinetics
im supposed to find the slope= -EA/R = triangle y/triangle x = (y2-y1) ________/(x2-x1)____________ how do i do this? is it the same as the slope that excel gave me? i have information from 3 different groups, and i have 3 x's and 3 y's, how do i solve this? the ...
October 16, 2010

chem lab
hi im doing a post lab sheet for chem class. and im having a little trouble. i have: temperature 12.6 C -> 285.6 K Time 816 sec but im supposed to find 1/T(K) it looks like my classmate did this: 12.6 x 285.6 = 3598.56 however they gave me the response to group 2 also: and ...
October 16, 2010

jessie
if im missing any information, please let me know. just simple steps would be really helpful!
October 15, 2010

jessie
hi im doing a post lab sheet for chem class. and im having a little trouble. we did an experiment where we put a mixture into a bath and checked to see how long a color would leave from the mixture. i have temperature 12.6 C -> 285.6 K Time 816 sec but im supposed to find 1...
October 15, 2010

Enthalpy of Formation
I got the answer to be 95.4 kj/mol I reversed the 1st equation to get an overall 187.6 kj = h1 then I just added that to H2 and I got the answer. But I still don't really understand the processes. If someone could explain that to me I would truly appreciate it.
May 16, 2010

Enthalpy of Formation
N2H4(g) + H2(g)--> 2 NH3(g) H1 = –1876kJ 3 H2(g) + N2(g)--> 2 NH3(g) H2 = –922 kJ The H.f for the formation of hydrazine: 2 H2(g) + N2(g)--> N2H4(g) will be______kj/mol I am very confused here. I thought I would just add H1 and H2 and divide by the molar ...
May 16, 2010

Unit Cells
I got it thank you! The A^3 was suppose to stand for ångström cubed...
May 9, 2010

Unit Cells
Copper has a unit cell volume of (47.453 A^3) and a face centered unit cell. How would I go about finding the volume of atoms within the unit cell? Would you use Avogadro's # somehow?
May 9, 2010

gen chem
that works! thank you so much!!
May 9, 2010

gen chem
yes, I figured that one out. Thanks so much for the help!
May 9, 2010

gen chem
2NO <-> N2 O2 initial .116 0 0 change -x +x +x equil .116-x x x
May 9, 2010

gen chem
yes I did, but im still not getting the right answer. I got .1136 which is not the correct answer.
May 9, 2010

gen chem
At 2273K, equilibrium constant for the reaction 2NO(g)<->N2(g)+O2(g) Kc=2.4x10^3 What would be equilibrim concentration of N2, if initial concentration of NO was 0.1160M?
May 9, 2010

gen chem
yes, it wants an actual value
May 9, 2010

gen chem
what would Qc be if the pressure of the container decreased by a factor of 2.417 for the following reaction? 4Hcl(g)+O2(g)<-->2Cl2(g)+2H2O(g) Kc=13.298 @ 753K
May 9, 2010

gen hem
what is the free energy change in kJ for the reaction below? 2NO3-(aq)+8H+(aq)+3Hg(l) <-->2NO(g)+4H2O(l)+3Hg2+(aq) E0=0.106V
May 8, 2010

gen chem
i tried that, apparently its not the right answer either =/.
May 8, 2010

gen chem
with n=10, im getting an answer of 0 when I do e^(k) i got lnK= (10)(96485)(-1.133)/(8.314)(298) lnK=-441.228 e^(-441.228)=0
May 8, 2010

gen chem
what is "n" and thank you so much for all the help!
May 8, 2010

gen chem
E cell is not given, just the E0 cell which is -1.133V
May 8, 2010

gen chem
what is the pK (=-logK)at 25C for the reaction below? Cl2(g)+6H2O(l)+5Cu2+(aq)<-->2ClO3-(aq)+12H+(aq)+5Cu(s) E0=-1.133V
May 8, 2010

gen chem
if the voltage of the cell is 2.0898V at 25C when [Mg2+] = 0.1945M and the pressure of H2 = 1.00atm, what is the pH? E0=2.3700V Mg(s)+2H+(aq)<--> Mg2+(aq)+ H2(g)
May 8, 2010

gen chem
what must be the current in amperes to plate out 7.437g of Al from am aqueous solution of Al3+ in 5.4x10^2 minutes?
May 8, 2010

General Chemistry
How much energy in kJ is realeased to form one mole of Cd 116(isotope) from protons and neutrons if the atom has a mass of 115.90476amu.
May 8, 2010

Molarity/molality
Ohhhhh That makes so much more sense. I didn't fully understand what the problem was asking. Thank you so very much =)
May 7, 2010

Molarity/molality
In regards to your latest post, I meant the very first step, not the step you did to check the answer. I'm assuming the first line is a typo?
May 7, 2010

Molarity/molality
And I'm a little unsure as to why after you find the mass of the solution 1059.269 you find how many g of H20 are in 1000 g of that soln. Why can't we just use the 1058.269 g? Was it to get the perfect 1000g (1kg) or was that unnecessary?
May 7, 2010

Molarity/molality
This makes more sense, but your first step is a little confusing. when I do 26.70 x 18.015 g H2O/mol I get 481.005 but when I do: 3.29 m x 18.015 g H2O/mol then I get your ans: 50.269 g H20
May 7, 2010

Molarity/molality
Thank you! I got the correct answer.
May 7, 2010

Molarity/molality
I found another post on this site, which explains a similar problem. :)
May 7, 2010

Molarity/molality
A 3.29 m solution of the solute H2O dissolved in the solvent acetone is available. Calculate the mass ( kg ) of the solution that must be taken to obtain 26.70 mol of H2O. m= molality I have no idea how to approach this problem, I'm not interesting in getting the answer, I...
May 7, 2010

CHemiStry!
its just the 2nd and 4th one
May 7, 2010

CHemiStry!
Select all ionic compounds in which the number of anions present is two. carbon dioxide X manganese(II) hydroxide mercury(II) carbonate X mercury(II) phosphate ammonia sulfur dioxide Hello, I know manganese(II) hydroxide mercury(II) phosphate both have two anions, however I am...
May 7, 2010

Chemistry
what would the freezing point be for a solution of 0.87M aqueous ammonia? The density of this solution is 0.992g/cm3
May 3, 2010

Hydrogen Bonding
The longer the hydrogen bond, do the Intermolecular Forces increase or decrease. So if molecule A has a H-bond with a length of 1.7 A and molecule B has a H-bond length of 1.8 A would molecule A or molecule B have a stronger IMF? It would seem that the longer the bond length ...
May 3, 2010

college Chemistry
If [K+] inside a cell is 25 times greater than a [K+] outside the cell, what is the difference in potential between the two sides of the cell wall? (this is a "concentration cell" style of problem)
May 1, 2010

CheMistry
Okay thank you that makes a lot more sense!
April 18, 2010

CheMistry
A stock solution was prepared by dissolving exactly 0.4000 g of pure ASA (180.16 g/mol) in 10.00 mL of NaOH and heating the solution to a gentle boil. After cooling to room temperature, the solution was poured into a 250-mL volumetric flask and diluted to the mark with DI ...
April 18, 2010

PHySICS
A rod 14.0 cm long is uniformly charged and has a total charge of -22.0 μC. Determine the magnitude and direction of the electric field along the axis of the rod at a point 36.0 cm from its center. ans:E = 1.59e6 N/C, pointing to the left equation:k_e(Q/L)(1/a-(1/(L+a))) ...
April 13, 2010

Intro Chemistry
oh thanks I get it now..
April 12, 2010

Intro Chemistry
tried using M1V1=M2V2 but without sucess
April 12, 2010

Intro Chemistry
_______g of MnSO4 H2O are needed to prepare a solution of 100.00mL of 0.100 M MnSO4. Thank You
April 12, 2010

Oxidation State
Give the oxidation sate for the monoatomic cobalt species whose electron configuration is the following:[Ar]4s0 3d6 Is the answer +3? Thank you!
March 6, 2010

Intro Chemistry
Thank you, I guess I got confused with Al and As :)
March 6, 2010

Intro Chemistry
I am reviewing my test and I having trouble figuring out the answer to the following question: List the following element symbols in order of decreasing exothermic electron affinity: Al, Ca, As _______>________>________ I wrote: Al>As>Ca (I got it wrong) I know ...
March 6, 2010

GenChem II
What mass of CsBr must be added to .500L of water to produce .4molality solution? What are mole fraction and mass percent? Here is my work and below I will post a question about it: 1 mol CsBr = 212.81g density of water = 1g/mL d=mv 1=x/500 x=500g of water --> solvent ....
February 18, 2010

Organic chemistry
How many grams of water would it take to quench 1 g of phenylmagnesium bromide?
February 12, 2010

bobpursley plz check
i m getting 9.77 g for Bi2S3 . no limiting reactant .. both are same .. can u plz conform
January 7, 2010

Chemistry
Can you repost #1 please. Thanks.
August 10, 2009

Chemistry
1) How many drops of 12M HCl would you add to 1.00 L of 0.100 M HC2H3O2 to make [C2H3O2-] = 1.0 x 10^-4 M? Assume that 1 drop = 0.050 mL and that the volume of the solution remains 1.00 L after the 12 M HCl is diluted. [Hint: What must be the [H3O+] in the solution?] 2. What ...
August 10, 2009

-
I'm sorry I made a typo it goes through a solution of Al(NO3)3 and that's why I mutliplied the m.w. of Al by 3 because you have 3 moles of Al per NO3
August 9, 2009

-
What mass of Al can be deposited by the passage of a constant current of 5.00 A through a Al(NO3)2 solution of 2.00 hours? My work: Q= I*t = 5 * 7200sec = 36000 36000/96458= .3732 .3732* 1/3 * (26.98*3) = 10.06g But this is wrong it's suppose to be 3.3.6g. why is that?
August 9, 2009

chemistry
thanx alot =)
March 16, 2009

chemistry
Consider a system consisting of a cylinder with a movable piston containing 10^6 gas molecules at 298K at a volume of 1L. Consider the following descriptions of this system: 1. Initial system 2. Starting from the initial system, the volume of the container is changed to 2L and...
March 16, 2009

CHEMISTRY
thanx a tons =)
March 2, 2009

chem help
ok thanks alot... the PartB asks for: What is the percent ionization of ammonia at this concentration?
February 28, 2009

chem help
sorry the 2nd question is the right one
February 28, 2009

chem help
Ammonia,is a weak base with a Kb value of 1.8x10^-5 .What is the pH of a 0.22M ammonia solution?
February 28, 2009

chem help
Ammonia,is a weak base with a Ka value of 1.8x10^-5 .What is the pH of a 0.22M ammonia solution?
February 28, 2009

chem help
You need to produce a buffer solution that has a pH of 5.08. You already have a solution that contains 10 mmol (millimoles) of acetic acid. How many millimoles of acetate (the conjugate base of acetic acid) will you need to add to this solution? The of acetic acid is 4.74.
February 28, 2009

chem
I DONT GET WHATS DONE.. DR.Bob22 - could u please explain this again..thank u
February 17, 2009

Chem
so wat do i do?
December 17, 2008

Chem
complete and balance the following decompition equations CaCO (heated) --> 3 please tell me how to do this and what exactly is suppose to be going through my head while doing this. I can balance these equations with no problem I just have no idea what to do...
December 17, 2008

Chemistry
How many atoms are there in 6.90 moles of sulfur (S)? Calculate the molar mass of a compound if 0.411 mole of it has a mass of 185 g. Know of any good sites that help answer these ? Or information on how to?
September 15, 2008

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