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October 23, 2016

# Posts by Chemistry

Total # Posts: 238

chemexamples
what are some good compounds(salts, acids,/bases) that are good conductors when dissolved in h2o
January 16, 2012

tommy
At a particular temperature, K = 3.75 for the following reaction. SO2(g) + NO2(g) SO3(g) + NO(g) If all four gases had initial concentrations of 0.870 M, calculate the equilibrium concentrations of the gases.
January 8, 2012

chemistry help
out of the pairs of orbitals which has a higher amount of energy 4f or 6s
December 30, 2011

chemistry question
Not just Na I mean all group 1 and 2 elements
December 27, 2011

chemistry question
why is it that when an unknown carbonate of group one or two (inc H) reacting w/ HCl, the mole ratio is 1:1
December 27, 2011

Laboratory Techniques
Calculate the number of moles K2CO3 of and MgCl2 in the 15 ml aliquots of reagent solution
November 14, 2011

Steph
Buffers work by converting _____ to ____.
November 1, 2011

science
the teacher instructed three students A,B,and C respectively to prepare a 50% (mass by volume) solution of sodium hydroxide (NaOH). 'A' dissolved 50 g of NaOH in 100 ml of water B dissolved 50g of NaOH in 100g of water while C dissolved 50g of NaOH in water to make ...
September 6, 2011

Shawn
How many milliliters of 0.355 M NaF solution are needed to react completely with 24.6 mL of 0.216 M CaCl2 solution? How many grams of CaF2 will be formed? The reaction is CaCl2(aq) + 2NaF(aq) → CaF2(s) + 2NaCl(aq)
July 8, 2011

Helen
How do you know which elements are solids, liquids, and gases at STP?
June 21, 2011

CHEM
NVVVMMMM its 4
April 30, 2011

CHEM
What is the number of "UNBOUND" electrons in H2O...its not 0 or 2....is it 1??
April 30, 2011

chemistry
A 79.9-L sample of a gaseous hydrocarbon, measured at 1.00 atm pressure and 25.0°C, is burned in excess oxygen, liberating 4.24 × 10^3 kJ of heat at constant pressure. What is the identity of the hydrocarbon? (R = 0.0821 L · atm/(K · mol)) Substance H&...
March 30, 2011

Chemistry
if you had 12 moles, just use a simple ratio (called a molar ratio): 12 mol KClO3 * (3 mol O2)/(2 mol KClO3) = 18 mol O2 ... this is your answer!
February 8, 2011

kassie
What is the major product of the reaction between methanol and (2R,3S)-2-bromo-3-methylpentane at room temperature?
February 7, 2011

chemistry
How do you write a redox reaction in an acidic environment for this? Cu^+2 + I- => CuI + I2 I understand that you get these equations for redox, but how do you put them in an acidic environment when there are no oxygens in the equation? 2I- => I2 + 1 electron 1 electron...
January 30, 2011

HELP
Calculate the change in energy when 665.0 g of CH3OH(g) completely reacts at a constant temperature of 300 K and constant pressure of 0.95 atm. R = 8.314 J/mol*K and R = 0.08206 atm*L/mol*K So i used the formula change in energy = change in H - nRT 90.7-51.9-38.8 its wrong i ...
January 27, 2011

Prove trig identity
re write the question properly sec^2 x? is there something there? there should be either x or thetha there and is it multplied
January 9, 2011

Prove trig identity
randy re check the question and use brackets to identify do u mean secant squared? or secant to the power of 2x-1
January 9, 2011

Math
-3,-2,4 use the number line
January 9, 2011

Algebra 1
x=-2/3
January 9, 2011

chemistry
what would be a diagram that we can use to idenitify an unknown substance using electrochemical data. we have a reduction table and ksp values and we also that the substance is either bromine or iodine
January 9, 2011

Math
6y+-4x + y -x 7y -5x
January 9, 2011

7z + 5 = 21 7z=21-5 7z=16 z=16/7
January 9, 2011

factor out 5 u get 5(4x^2+8x +3) = 0 5(4x^2+2x+6x+3)=0 5(2x(2x+1)+3(2x+1))=0 5(2x+1)(2x+3)=0 x=-1/2 or x=-3/2
December 13, 2010

chem
Excess fluorine, F2(g), reacts at 150°C with bromine, Br2(g), to give a compound BrFn. If 423 mL Br2(g) at 150°C and 748 mmHg produced 4.20 g BrFn, what is n? Predict the shape of this molecule using the VSEPR model.
December 13, 2010

chem
A molecular compound is composed of 58.8% Xe, 7.2% O, and 34.0% F, by mass. If the molecular weight is 223 g/mol, what is the molecular formula? Draw the correct Lewis structure. Predict the molecular geometry using the VSEPR model.
December 13, 2010

chem
A gaseous compound has the following composition by mass: C, 25.0%; H, 2.1%; F, 39.6%; O, 33.3%. Its molecular weight is 48 g/mol
December 13, 2010

chemistry
An ionic compound has the following composition (by mass): Mg, 10.9%; Cl, 31.8%; O, 57.3%. What is the formula and name of this compound?
December 13, 2010

chemistry
Consider the hypothetical elements X and Y. Suppose the enthalpy of formation for the compound XY is ƒ{336 kJ/mol, the bond energy for X2 is 414 kJ/mol, and the bond energy for Y2 is 159 kJ/mol. Estimate the XY bond energy in units of kJ/mol.
December 13, 2010

chemistry
What is the lattice energy of NaBr? heat of formation of NaBr = -362 kJ/mol heat of sublimation for Na = 107.30 kJ/mol ionization energy for Na = 496 kJ/mol bond dissociation energy for Br2 = 190 kJ/mol electron affinity of Br = -325 kJ/mol heat of vaporization for Br2 = 30.90...
December 4, 2010

chemistry
it worked now, thank you!
December 3, 2010

chemistry
9904.7 is the answer but I already tried that and its not working
December 3, 2010

chemistry
Given the reaction 3C(s) + 4H2(g) + 5O2(g) ---> 3CO2(g) + 4H2O(l) ÄH= -2323.7 kJ How much heat would be released when 34.1 g of H2 react?
December 3, 2010

Kelsie
name the element wsith the atomic number z= 15 and the atomic mass number 31. How many electrons does the neutral of this lement have? How many neutrons does the neutral atoms of this element have? I know the element with the atomic number of 15 and atomic mass of 31 is ...
November 8, 2010

tere
what did i do wrong? i need to find lowest vapor pressure. a 0.13 m FeCl3 b 0.50 m sucrose c 0.24 m NaNO3 d 0.15 m Na2PO4 so i solved. a 4 x 0.13 = 0.52 b 1 x 0.50 = 0.50 c 5 x 0.24 = 1.2 d 7 x 0.15 = 1.05 i chose C but the answer is A. did i do something wrong?
October 16, 2010

muah
using only words and no numbers how would i explain the steps necesarry to show how many kilograms are in a milligram? thanks :D
September 26, 2010

muah
With out using numbers just words what are the steps necesarry to show how many kilograms are in a milligram
September 26, 2010

muah
explain why the name of the insect millipede doesnt follow SI conventions? please help me i cant find this any where in my text. I would be very happy if you did help. :D
September 26, 2010

gen chem
What is the boiling point in K of Zn, if the entropy change for evaporation of .8564 mole at its boiling ponit is 95.067K? The heat of vaporization of Zn is 131jk/mole.
May 9, 2010

gen chem
im getting 1.54e-6
May 9, 2010

gen chem
thanks for the help but im still not getting the right answer
May 9, 2010

gen chem
The free energy change for dissolution of CaSO4 at 25C is 28.774kJ/mole. What is the solubility of this compound. i got ksp lnK = deltaG/RT lnK= 28774/(-8.31*298) Ksp = 2.39e-12 i don't know waht to do after this..
May 9, 2010

gen chem
suppose a compound could point in any of the three directions in the solid and still have the same energy. how many molecules would there be if the total entropy of a solid sample of this compound was 3.48x10^-9 j/k
May 9, 2010

gen chem
calculate [H+] if [OH] is 1.688x10^-3
May 9, 2010

discuss the kinetic theory of gases and proof that the equation pv =1/3 mv2
April 13, 2010

chemistry (quatatative analysis)
BARIUM IODATE CAN BE DISSOLVED IN WATER.
March 26, 2010

chemistry
CH3 CH3-C-CH3 CH3CH2CH2-C-CH2CH2CH2CH3 CH3 give the IUPAc name for this compound? is it 4-methyl-4-tert-methyloctane?
March 5, 2010

Im organic chemistry
What hapens you moving from left to right in a periodc table?
December 16, 2009

To bobpursley
Thank you once again for helping me!!!!
November 3, 2009

To bobpursley
two more questions.... 1. so when you use the superscript ^- that is the same as saying ^-1 ? 2. what are OH^-1 and H^+1 in the equations? (liquid , or gas)
November 3, 2009

To bobpursley
okay..... K^+1 + OH^-1 + H^+1 + Br(not sure which ionization number to put here)-> K^+1 + Br + H20 (l) also, i am not sure what the other ions are.... (aq)? is my guess Then the net ionic equation is... OH^-1 + H^+1 -> H2O (l)
November 3, 2009

To bobpursley
Thank you so much for giving me a step-by-step! I am homeschooled so i have no one to ask. I have had trouble with this and you are the only thing that has clearly told me how to do this. I only asked bob pursley b/c he gave me the answer last time and i was fustrated and ...
November 3, 2009

To bobpursley
i do not know how to break down the ions when i know that they are soluble. for example...Ca(HO)2 is soluable but i don't know what to do with the two or what superscripts to use...
November 3, 2009

To bobpursley
Is the answer you gave the ionic and net ionic equation....
November 3, 2009

To bobpursley
You helped me earlier today whith one of these problems... and i have two more...... What is the ionic and net ionic equation? 1. Ca(HO)2(aq)+ Na2CO3(aq)-> CaCO3 -> (s)+ 2NaOH (aq) I don't understand why there are two arrows? This is what i have so far... Ca+2OH+Na2(...
November 3, 2009

ChemChem
Hi, please help! Question: Farmers added Calcium hydroxide to soil one morning. They then planned to add Ammonium chloride fertilisers to the soil immediately. However, the instruction label on the packet of fertilisers read: "Do not add fertiliser immediately after ...
November 2, 2009

Chemistry Octane Combustion
Write the balanced equation for the combustion of octane (C8H18). Assuming that gasoline is 100% octane, with a density of 0.692 g/mL, what mass of CO2 is produced by combustion of 1.7 1010 gal of gasoline? Need help on how to get started, I have the balanced equation...
September 15, 2009

Chemistry
Got it now, thanks a ton.
September 15, 2009

Chemistry
Please elaborate on step 3. The balanced chemical equation is: Fe2O3(s) + 2 Al(s) -> 2 Fe(l) + Al2O3(s) After step 2 I have .32 moles Fe.
September 15, 2009

Chemistry
Fe2O3(s) + 2 Al(s) 2 Fe(l) + Al2O3(s) Suppose we want to make 18.0 grams of iron. We must figure out how much starting material we need. This is a three-step calculation. Let's go through these steps one-by-one to calculate the mass of Fe2O3 that we must start with. ...
September 15, 2009

Chemistry
1355.37
September 13, 2009

Chemistry
Vitamin B12, cyanocobalamin, is essential for human nutrition. It is concentrated in animal tissue but not in higher plants. Although nutritional requirements for the vitamin are quite low, people who abstain completely from animal products may develop a deficiency anemia. ...
September 13, 2009

Sara
okie thank you =)
August 9, 2009

Sara
Neither Ka nor Pka was given
August 9, 2009

Sara
how did you calculate pKa because this is a practise question for my test and we won't be given the value. so how would you calculate it?
August 9, 2009

Sara
I'm making a mistake in using that equation: n (CH3COO-)= .0132*.2 = .oo264 ..does that mean that CH3COOH also has the same n? ph= pKa +log(Conjugate Base/ Weak Acid) 4.2= pKa + log (.00264/ .00264) since i have n the same it doesn't work. How do you calculate n?
August 9, 2009

Sara
How many mL of .200M acetic acid are mixed with 13.2mL of.200M sodium acetqte to give a buffer with pH=4.2
August 9, 2009

Chemistry
me again 8. You are given two beakers, A and B, with colorless liquids in htem. What two tests would you perform to determine which one is a strong acid and which one is a weak acid? Be specific with the test and the results as well as how you would determiine which is which. ...
April 7, 2009

Chemistry
so i got a test and like usual my teacher didn't teach me half of the stuff that's going to be on it so he gave us a pretest of what is going to be on it and an answer key and i got several questions 13.) what is the pH of a formic acid if the concentration is .00055 M...
April 7, 2009

Math
radius increasses by 25000 solve for dimater then solve for circumference i think
April 7, 2009

chemistry
The reaction converting glycerol to glycerol-3-phosphate is energetically unfavorable by 9.2kJ. The reaction of ATP with water to yield ADP, hydrogen phosphate ion, and hydrogen ion is energetically favorable by 30.5kJ. These reactions are coupled so that the overall process ...
March 19, 2009

chemistry
thanx alot =)
March 16, 2009

chemistry
i tried dat..n got: AlPO4(s)+H3O^+(aq)<=>Al^3+(aq)+HPO4^2-(aq) buh for sum reason its not accepting the answer
March 16, 2009

chemistry
AlPO4(s)<=>Al^3+(aq)+PO4^3-(aq) PO4^3-(aq)+H3O^+(aq)<=>HPO4^2-(aq)+H2O(l) What is the net ionic equation for AlPO4(s) dissolving in H3O^+(aq)?
March 16, 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
A solution of Na2CO3 is added dropwise to a solution that contains 1.34×10−2M Fe^2+ and 1.33×10−2M Cd^2+ . What CO3^2- concentration of is need to initiate precipitation? Neglect any volume changes during the addition.
March 14, 2009

Chemistry
correction: initially 1.22*10^-4 mols of Fe(II) were present
March 14, 2009

Chemistry
I converted CN^- to moles iron(II)which is 2.75*10^-5, and initially 1022*10^-4 mols of Fe(II) were present. now i don't get the next step ..
March 14, 2009

Chemistry
The average human body contains 5.30L of blood with a Fe2+ concentration of 2.30×10−5M . If a person ingests 11.0mL of 15.0mM NaCN , what percentage of iron(II) in the blood would be sequestered by the cyanide ion?
March 14, 2009

CHEMISTRY
PartA: Ammonia,is a weak base with a Ka value of 1.8x10^-5 .What is the pH of a 0.22M ammonia solution? PartB: What is the percent ionization of ammonia at this concentration? I got the answer for PartA which is pH=11.3. but i cant slove PartB..HELP!!!
March 2, 2009

Chemistry
Do you think you know how to figure out this one: Sorry about that The chemical 5-amino-2,3-dihydro-1,4-phthalazinedione, better known as luminol, is used by forensic scientists in analyzing crime scenes for the presence of washed-away blood. Luminol is so sensitive that it ...
February 11, 2009

Chemistry
Nevermind I figured it out with your help. The answer was 2.94. Thank you so much!
February 11, 2009

Chemistry
Are you saying that the molar concentration is .005
February 11, 2009

Chemistry
Ammonia has the formula NH3. Household ammonia is a dilute aqueous solution of NH3 . Aqueous ammonia is a base that can neutralize acids. If 18.4mL of 0.800 M HCl solution are needed to neutralize 5.00 mL of a household ammonia solution, what is the molar concentration of the ...
February 11, 2009

Chemistry
Sorry about that The chemical 5-amino-2,3-dihydro-1,4-phthalazinedione, better known as luminol, is used by forensic scientists in analyzing crime scenes for the presence of washed-away blood. Luminol is so sensitive that it can detect blood that has been diluted 10,000 times...
February 11, 2009

Precipitates
If i used NaCl to try to precipitate Ag+ from a solution, will it be as effective as HCl?
November 16, 2008

chem
how can you fill a flask with pure oxygen without mixing it with air
November 1, 2008

REETA
A 2.10 mol sample of oxygen gas is confined to a 5.10 L vessel at a pressure of 7.99 atm. Find the average translational kinetic energy of an oxygen molecule under these conditions in (j/mol) When i was working this out i tried using pv=nrt to find the temperature which i got ...
October 21, 2008

chemistry
What is the difference between Keq and the term of [prod]pr / [react]pr?
September 1, 2008

scsu
What is the weight per volume percent (i.e. % density) of 0.5522 g acetic acid in the 10.00 mL sample?
April 21, 2008

kim
a gaseous hydrocarbon reacts completely with oxygen gas to form carbon dioxide and water vapor. given the following data, determine (delta)HoF for hydrocarbon: (delta)Horxn=-2044.5kj/mol hydrocarbon (delta)HoF CO2= -393.5kj/mol (delta)HoF H2O = -242kj/mol denstity of CO2 and ...
April 20, 2008

Jack
how does cross linking alter the properties of a polymer?
February 28, 2008

Jason
I understand that polymers are long chain 500-20,000 repeating units, but I don't know: what car components are made of polymers?
February 28, 2008

My problem is calculate the molarity of HCl and NaOH (molarity of acid)x(volume of acid)=(molarity of base)+(volume of added base) HCl=acid NaOH=base HCl volume = 25mL=0.025L NaOH=67.05mL=0.06705 molarity = moles of solute Liters of a solution M=0.015000 moles of NaOH 0.06705L...
February 19, 2008

Chem
Directions: Use the principles of atomic structure and/or chemical bonding to explain each of the following. In each part, your answer must include references to both substances. Problem: The carbon-to-carbon bond energy in c2h4 is greater than it is in c2h6. Any help is ...
November 19, 2007

Mike
N2 + 3H2 --> 2NH3 At 25Â°C (delta)Ho = -92.22 kJ and (delta)So = -198.53 J/K. Using this information, calculate the equilibrium constant for the reaction at 2.43x10^2Â°C. (R = 8.314 J/K) Apparently the way I'm doing it is wrong: I divide 198.53 by ...
November 17, 2007

Lauren
-6783.72 J
November 16, 2007

Lauren
wouldnt it be 4.184J/g * degrees C so 4.184 J/ 162 g H2O * 10 degrees C = ?
November 16, 2007

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