# Posts by Chemistry

Total # Posts: 253

Chemistry
What volume of 0.250M KOH is required to titrate 2.30 x 10^3 mol of the weak acid H2C2O4 ? I know the answer is 18.4, but can you show the process?

Chemistry
Explain the Hyberdaization scheme for the central atom&the molecular geometry of CO2.

Chemistry
A 53 mL sample of a solution of sulfuric acid is neutralized by 37 mL of a 0.18 M sodium hydroxide solution. Calculate the molarity of the sulfuric acid solution. Answer in units of mol/L

Chemistry
Calculate DeltaHrxn for the following reaction: C + H2O --> CO + H2 Use the following: C + O2 --> CO2 DeltaH = -393.5 kJ 2CO + O2 --> 2CO2 DeltaH = -566.0 kJ 2H2 + O2 --> 2H2O Delta H = -483.6 kJ DeltaHrxn = ?

cemistry
thx but wat is a good way to remember it

cemistry
how to identify bond angles

chemhelp
ok, thanks

chemhelp
could i use it safely at home

chemhelp
is LiCl toxic?

chemistry
what is the chemical balance equation for the following: Magnesium metal and hydrochloric acid copper matal and hydroshloric acid potassium hydroxide and acetic acid

chemexamples
where can I access this? and are they all good conductors

chemexamples
any more other than these that can be easily accessed

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

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.

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

chemistry question
Not just Na I mean all group 1 and 2 elements

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

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

Steph
Buffers work by converting _____ to ____.

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 ...

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)

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

CHEM
NVVVMMMM its 4

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

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&...

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!

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

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...

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 ...

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

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

Math
-3,-2,4 use the number line

Algebra 1
x=-2/3

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

Math
6y+-4x + y -x 7y -5x

7th Grade
7z + 5 = 21 7z=21-5 7z=16 z=16/7

11th grade
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

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.

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.

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

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?

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.

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...

chemistry
it worked now, thank you!

chemistry
9904.7 is the answer but I already tried that and its not working

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?

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 ...

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?

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

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

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

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.

gen chem
im getting 1.54e-6

gen chem
thanks for the help but im still not getting the right answer

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..

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

gen chem
calculate [H+] if [OH] is 1.688x10^-3

ChEMISTRY (Help please)
discuss the kinetic theory of gases and proof that the equation pv =1/3 mv2

chemistry (quatatative analysis)
BARIUM IODATE CAN BE DISSOLVED IN WATER.

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

ENVIRONMENTAL CHEMISTRY
Which one of the following statements is incorrect? Why? A. “Oxygen (O2) is a strong oxidant (oxidizing agent).” B. “Oxygen (O2) is an active oxidant (oxidizing agent).”

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

To bobpursley
Thank you once again for helping me!!!!

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)

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)

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 ...

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...

To bobpursley
Is the answer you gave the ionic and net ionic equation....

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(...

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 ...

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...

Chemistry
Got it now, thanks a ton.

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.

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. ...

Chemistry
1355.37

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. ...

Sara
okie thank you =)

Sara
Neither Ka nor Pka was given

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?

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?

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

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. ...

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...

Math
radius increasses by 25000 solve for dimater then solve for circumference i think

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 ...

chemistry
thanx alot =)

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

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)?

chemistry
thanx alot =)

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...

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.

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

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 ..

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?

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!!!

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 ...

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

Chemistry
Are you saying that the molar concentration is .005

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 ...

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