Tuesday
September 30, 2014

Posts by GK


Total # Posts: 640

CHEMISTRY
Ammonia has a Kb of 1.8x10^-5 (NOT the Ka) Kb = [NH4+][OH-] / [NH3] Let [OH-] = [OH-] = x Then, 1.8x10^-5 = x^2/(0.22-x) We can get an adequate approximate solution by assuming 1.8x10^-5 = x^2/(0.22) x = [OH-] = 0.00199 pOH = -log(0.00199) = 2.7 pH = 11.3 (your answer...
March 2, 2009

chemistry
No, the are not the same. The Combined Gas Law is: P1V1/T1 = P2V2/T2 The Ideal Gas Law is: PV = nRT Your chemistry textbook should explain the difference. The most importance difference is that in the Combined Gas Law, the amount (moles) of gas are assumed to be constant. In ...
March 2, 2009

chemistry
71.3 mL is the final volume, not the amount of water added to achieve that volume. Does that help?
March 2, 2009

intro chemistry
Are you asking about a chemical reaction between aldehydes/ketones and alcohols? If so, they do react to form (hemi)acetals) and (hemi)ketals. Are you asking about hydrogen bonding? That involves the attraction between a hydrogen in a H-O- group and an O in a different H-O- ...
February 25, 2009

Chemistry- please check my work
•Find the moles of MgSO4 by dividing 95.00g by the formula mass of MgSO4. •Multiply the moles of MgSO4 by 3 ions / mole to get the moles of ions in solution. •Convert 95g of H2O to moles. •Add moles of ions to moles of H2O to get total moles. •The ...
February 23, 2009

Chemistry
Let the fraction of Copper-65 = x. Then Copper-63 would be (1-x) We set up an equation for the "weighted average" of copper based on the individual isotopes of copper: 62.93(1-x) + 64.93x = 63.54 Solve for x to get the % of Cu-63 Use (1-x) to get the % of Cu-65
February 23, 2009

Chemistry
A protein is a long chain of amino acids linked together by "peptide links". It is a biological polymer molecule. Body tissues are made of proteins, not individual amino acids which would not give them the structural strength they need. The chemical functions of ...
February 23, 2009

Chemistry
Ca(OH)2 + 2HCl --> CaCl2 + 2H2O Find the moles of Ca(OH)2 = grams / formula mass moles of HCl = (2)[moles of Ca(OH)2] <-- see equation. volume of HCl = moles HCl / molarity of HCl
February 19, 2009

Chemistry
Find the moles of OH- = moles NaOH moles OH- = (liters)(molar concentration) moles of HX = moles of OH- molar mass = (grams of HX) / moles HX
February 19, 2009

Chemistry
You can find a proof in the web page below: http://www.tutorvista.com/content/physics/physics-iii/rigid-body/diatomic-molecule.php The symbols used are different but equivalent to the ones you are using. The general formula is not given explicitly but it is applied anyway.
February 16, 2009

Chemistry
Density = Mass / Volume Multiplying both sides by bolume, Volume x Density = Mass Dividing both sides by density, Volume = Mass / Density V = 24 g / 12 g/mL = ____?
February 15, 2009

Chemistry
•Moles of NH3 = (0.0500L)(0.100mol/L) = 0.00500 mol NH3. •0.0500 L + 0.0200 L = 0.0700 L total volume •Moles of NH3/Liter = 0.00500 mol NH3/0.0700 L) = 0.07143 mol/L = 0.07143 M NH3 (before reacting with HCl) •(0.250mol/L)(0.0200L)/(0.0700L) = 0.07143 M HCl...
February 15, 2009

Chemistry
Sorry for a bad sentence in my answer: "Since the amount of Al needed is LESS that the amount available, aluminum is the LIMITING REAGENT. ". It should read: Since the amount of Al needed is MORE that the amount available, aluminum is the LIMITING REAGENT.
February 15, 2009

Chemistry
The reaction for the formation of aluminum oxide is: 4Al + 3O2 -->2 Al2O3 Moles of Al = 10.00g Al / 26.98 g/mol = 0.3706 mol Moles of O2 = 10.00 g O2 / 31.999 g/mol = 0.3125 mol O2. (mol. Al)/(mol.O2) = 0.3706 / 0.3125 = 1.186 (based on amounts used) (mol. Al)/(mol.O2) = 4/...
February 15, 2009

Chemistry
Gamma rays emitted by Po-210 ionize air. Ionized air is a better conductor of electricity than normal air. The increased conductivity of ionized air helps discharge static charge into the ground.
February 15, 2009

college-- chemistry
(a) The energy of a photon is given by: E = hf h = Planck's constant (look it up) f = frequency = speed of light / wavelength f = (3.00x10^8 m/s) / (0.15m) = _____? E = ______? (b) ∆T = T2 - T1 = ____? Heat needed = (4.18 J/g.C)(grams H2O)(∆T) Heat = _________...
February 15, 2009

college: Chemistry
This question should have been posted on the PHYSICS board.
February 15, 2009

College: Chemistry
•Convert the minutes to seconds. •Multiply (photons/sec) by number of seconds to get the total number of photons. •Divide total joules by numer of photons to get the energy of a photon. • E(photon) = h*f (f = freq.) Substitute E and h into the above ...
February 15, 2009

chemistry
CH3NH2(aq) + H2O <=> CH3NH3+(aq) + OH-(aq) Kb = [CH3NH3+][OH-] / [CH3NH2] = 4.38x10^-4 Let [OH-] = x, and [CH3NH2] = 1.00M x^2 / (1.00-x) = 4.38x10^-4 If x is much smaller than 1.00, the above equation can be simplified to x^2/1.00 = 4.38x10^-4 x = sqrt(4.38x10^-4) solve...
February 14, 2009

osmotic pressure chemistry.
I thought I was answering: http://www.jiskha.com/display.cgi?id=1234647827
February 14, 2009

osmotic pressure chemistry.
For a given mass of solute per liter of solution, the larger to formula mass, the lower the osmotic pressure. Osmotic pressure depends on molar concentration. A large molar mass would tend to produce a lower concentration in terms of moles of particles per liter.
February 14, 2009

osmotic pressure chemistry.
Thanks, Ms.Sue. Changing browsers seems to cause confusion.
February 14, 2009

chemistry...Please Help
Here is my take on the question without any guarantees: 1. Reverse and multiply by 2 N2(g)+ 1/2O2(g)<---> N2O(g) Kc=2.7*10^-18 2N2O –> 2N2 + O2 K1 = [1 / 2.7*10^-18]^2 2. Reverse and multiply by 2 N2O4(g)<----> 2NO2(g) Kc= 4.6*10^-3 4NO2 –> 2N2O4 K2...
February 9, 2009

Chemistry
These are typical reactions between and acid and a bicarbonate, and an acid and a base. Sodium formate (a salt) and H2O are forming in both cases. CO2 is forming typically when a base reacts with a bicarbonate or a carbonate. HCOOH + NaHCO3 ---> HCOONa + H2O + CO2 HCOOH + ...
February 4, 2009

Chemistry
Amines (organic bases) react with HCl to form ammonium salts. Organic salts dissolve in water.
February 4, 2009

Chemistry
Judge for yourself. The reaction is: NH4NO3 ---> N2O + 2H2O
February 4, 2009

Chemistry
Acetaminophen is a phenol and a phenylamine. One of them has a high solubility in water.
February 3, 2009

Chemistry
Look at the structural formula of acetaminophen. Is it an acid. If it is, it may dissolve in the basic solution by reacting with it.
February 3, 2009

chemistry
Here is the 2nd part of the answer: Mg(s) + O2(g) ---> MgO(s) You should be able to translate that into a word equation.
February 3, 2009

english
un scramble the following words kerba ni that means enter illegally
February 2, 2009

chemistry
The mole fraction of each component = 0.5 The vapor pressure of the mixture is: P = (0.5)(22) + (0.5)(75) = ____ mm X(benzene vapor) = P(benz. vapor)/P X(benzene vapor) = (0.5)(75)/P
February 2, 2009

chemistry
See: http://www.jiskha.com/display.cgi?id=1233540017#1233540017.1233552198
February 1, 2009

chemistry
From the information given, I think it is the enthalpy, ∆H, you need to find for the overall process. You have the following calculations: 1. Heating of ice from 240 to 273 K: ∆H1 = (36 j/mol.ºK)(4.0 mol)(273K-240K) 2. Melting of ice: ∆H2 = (4.0mol.)(5....
February 1, 2009

chemistry
W(isothermal) = nRT*ln(V2/V1) or W(isothermal) = nRT*ln(P1/P2) See also: http://www.diracdelta.co.uk/science/source/i/s/isothermal%20expansion/source.html
February 1, 2009

Chemistry
SO2 forms H2SO3 in water: Step 1 H2SO3(aq) <=> H^+(aq) + HSO3^-(aq) K1 = [H+][HSO3^-]/[H2SO3] = 1.71x10^-2 Step 2 HSO3-(aq) <=> H^+(aq) + SO3^-2(aq) K2 = [H+][SO3^-2]/[HSO3^-] = 6.0x10^-8 The above sequence shows that Step 1 is the primary source of hydrogen ions ...
February 1, 2009

Chemistry
In any electrolytic (salt or acid ) solution, electrons are transferred from Fe to O2 in a series of steps. Here is the overall reaction: 2Fe + O2 + 2H2O ---> 2Fe(OH)2 Acid reduces the concentration of OH- ions which drives this reaction faster. The Fe^+2 ions in Fe(OH)2 ...
February 1, 2009

Physics
(a) Vf^2 = Vo^2 + 2gy since Vo = 0, Vf^2 = 2gy Substitute and solve for Vf (b) y =(1/2) gt^2 Substitute and solve for t
January 30, 2009

physics
Your answer should be in watts in the range of 20 to 90 watts. You should be familiar with the symbols I used and the appropriate units for each.
January 30, 2009

physics
Since the box is pulled at a constant speed, the force applied is equal to the force of friction. F = F(friction) = µ*m*g Power generated = P = Fv
January 30, 2009

Physics
1 km/h = 1000m/3600s = ________ m/s Now you should be able to do the conversion for 94 km/h
January 30, 2009

chemistry
The first and fourth carbon atoms are sp2 hybridized. The second and third carbon atoms are sp hybridized. There is no need to assume the hydrogen atoms are hybridized. Hybridization is a scheme to explain the geometry around a central atom bonded to two or more other atoms. ...
January 30, 2009

chemistry
Here are some guidelines on equilibria involving gases: 1. Increasing the pressure causes a shift toward the side with the smallest number of gas molecules. 2. Increasing the temperature causes a shift in the direction of the endothermic change. That could be the forward or ...
January 28, 2009

chemistry
There is more than one reaction in which nitric oxide,NO, could be a reactant of product. Which reaction is your question about? What is the chemical equation for it?
January 28, 2009

chemistry
A. Atoms with incomplete valence shells (outer electron shells) lose, gain, or share electrons in a way that would give them a complete valence shell. That lowers potential energy and increases stability of atoms forming ionic or covalent bonds. B. The control in an ...
January 26, 2009

Organic chemistry
Impurities that dissolve in water or whatever liquid you used to wash the crystals. Since you are not giving us any background on what the crystals were or how they were produced, we can't tell specifically what was removed. Read your procedure and other background ...
January 23, 2009

Organic Chemistry
What reaction? It would be nice to know.
January 21, 2009

chemistry
K = [SO3][NO / [SO2][NO2]] = 3.75 Let the moles of each reactant = x [0.840+x][0.840+x] / [0.840-x][0.840-x] = 3.75 a) Solve for x. b) To get the concentration of each reactant, subtract the value of x from 0.840M. c) To get the concentration of each product, add the value of ...
January 15, 2009

Chemistry
pH = pKa + log{[A-]/[HA]} or pH = pKa + log{[NaA]/[HA]} if pH = pKa, then {[log{[NaA]/[HA]} = 0 or [NaA] = [HA] The reaction between NaOH and HA is: NaOH + HA --> NaA + H2O Since we start with no NaA, we must add enough NaOH so that [NaA] = [HA] That happens when we ...
January 12, 2009

CHEMISTRY
See the answer at: http://www.jiskha.com/display.cgi?id=1231796296
January 12, 2009

chemistry
Light (a photon) is emitted by an atom when an electron jumps from a higher to a lower energy level. According to the Bohr theory of the atom, the energy levels that an electron can occupy in a atom are discreet. If the energy levels are discreet, their differences (photon ...
January 12, 2009

Chemistry
At room temperature, there is no reaction.
January 11, 2009

chemistry
Look up the atomic mass of molybdenum, Mo. Look up the atomic mass of carbon, C. Divide the first mass by the 2nd mass. Round off to the nearest whole number. The answer is less than 10 atoms of carbon.
January 11, 2009

Chemistry
There is no reaction to balance. Copper metal does not react with copper(II) sulfate: CuSO4(aq) + Cu(s) ---> No Reaction
January 11, 2009

chemistry
In what reaction? What are the amounts of each reactant in that reaction?
January 11, 2009

chemistry
Yes in F2 in which the eletronegativity difference between the two fluorine atoms is 0.
January 11, 2009

chemistry
A small electronegativity difference indicates that the covalent bond is not very polar.
January 11, 2009

chemistry
Not much about the strength of the bond but a lot about the bond polarity.
January 11, 2009

12th grade Chemistry
The total volume of the mixture is: 5 + 3 + 3 = 11 mls = 0.011 L I used 0.010 L by mistake. It should be replaced by 0.011 L. This will case a small change in the concentrations of Fe+3 and SCN-
January 11, 2009

12th grade Chemistry
The equilibrium reaction is: Fe+3(aq) + SCN-(aq) <=> FeSCN+2(aq) If the reaction to the right goes to completion, the final concentration of Fe+3(aq) can be found as follows: A. Assuming a reverse reaction occurs and equilibrium is established: 1. We can find [Fe+3] by ...
January 11, 2009

crt 205
This is not a blog for expressing world views. It is a homework help forum. If you have a specific question related to a skill you must develop in a science class, we may be able to help you. Scientific theories are not validated through discussion or debate. Validation ...
January 9, 2009

Chemistry
Elements in Group IIA of the periodic table can replace one of the hydrogen atoms in H2O to produce a hydroxide and H2 gas. Example: Ca(s) + H2O ---> Ca(OH)2 + H2 Ca(s) + 2H2O ---> Ca(OH)2 + H2 (balanced) Other elements in the same column as Ca react in a similar way. ...
January 7, 2009

chemistry
The two initial compounds are made of electrically charged particles, ions. Pb(NO3)2 represents one Pb^+2 ion and two NO3^-1 ions. LiCl represents Li^+1 ions and Cl^-1 ions. When the two compounds are dissolved in water, any positive ion can associate with any negative ion in...
January 7, 2009

Chemistry...Please Help
(a) I will give you one of these two: NaHCO3(s) ---> Na+(aq) + HCO3-(aq) (b) If you are asked that question, you must have access to printed materials that give the answers. (c) Same as above answer. (d) HCl + NaOH ---> NaCl + H2O (several other possible examples using ...
January 6, 2009

Science - gr. 10 physics
Calculate the area under the velocity-time graph.
January 5, 2009

chemistry HELP
heat = (sp. heat)(grams)(temp. change) or q = (C)(m)(Tf-Ti) Heat released by Cu = Heat absorbed by H2O (C)(46.2g)(95.4C-21.8C)= (4.18J/g.C)(75.0g)(21.8C-19.6C) Solve for C to get the specific heat of copper.
January 2, 2009

Chemistry
If we include the water of hydration, the unbalanced chemical reaction becomes: Na2B4O7.11H2O + H2SO4 = H3BO3 + Na2SO4 + H2O (The coefficient of H2O on the right side is 6. You can finish balancing it to convince yourself it is a viable chemical equation)
January 1, 2009

Chemistry
DrBob gave you a good start. Here is a little more information in the form of an unbalanced chemical equation: Na2B4O7 + H2SO4 + H2O = H3BO3 + Na2SO4
January 1, 2009

Chemistry
MgO has no molecular shape because it is not made of molecules. It is an ionic solid. The crystal structure of MgO is similar to that of NaCl (cubic cf8).
December 29, 2008

Chemistry
a) Look up the molar heat (enthalpy) of fusion of water. b) Convert 25 grams of H2O to moles by dividing by the formula mass of H2O. c) Multiply (a) times (b)
December 28, 2008

Water Chemistry
a) Look up the atomic mass of P. b) Calculate the formula mass of the phosphate ion, PO4^2-. Multiply 0.50 mg/L by the fraction of (a)/(b). [The above fraction is roughly 31/95, not 30/64]
December 27, 2008

chemistry
Here are some tests that may help: CuSO4 + NH3 ----> deep purplish blue color when an excess of NH3 is used. That would confirm NH3. If no clues were given for the other colorless solution, it would not be easy to identify it. Cu(OH)2, unlike CuSO4, has low solubility in ...
December 27, 2008

organic chemistry
This sounds like a chromatography lab question. You have not told us what the stationary phase is or what solvent is used. Rf is an an experimentally determined value that helps compare speeds of migration of components of the sample. This speed would depend on intermolecular ...
December 27, 2008

Biochemistry
The reaction, depending on the conditions, is: (H2N)2CO ---> NH3 + HNCO The test you describe sounds like the biuret test for the peptide link. Both, urea and proteins have peptide links and give a positive test. If you have done this experiment, you should know the ...
December 25, 2008

physics
1. Momentum for part A: y = (Vo)t - (1/2)(9.8m/s^2)t^2 Substitute the values for y and t which are given. Solve for Vo, the initial downward velocity. Multiply the value of Vo by 0.5 kg to get the initial momentum down of A. 2. Momentum for part B: y = (1/2)gt^2 = 45m for its ...
December 21, 2008

Chemistry help needed
(0.99)(1.22g.soln/ml) = 1.2078 g pure acid / mL original soln. To get 100.0 g of pure acid: (100.0g) / 1.2078 g acid / mL = 82.8 mls original solution. The total weight of that solution is: (82.8 mls)(1.22g/ml) = 101g) (Let the diluted solution contain 100.0g pure acid = m) ...
December 17, 2008

Physics - Fluids
(a) Q1 =(sp,heat)(grams)(T1-T2) I think the initial temperature, T1, should be given. As it stands, we have two unknowns, Q1 and T1. (b) Q2 = (watts)(seconds) (c) Q3 = Q2-Q1 (d) Q3 = (sp.heat of air)(grams air)(∆T) Substitute values from previous steps, solve for (∆T)
December 17, 2008

Physics
Not sure that the premise of your question is correct. If the rockets are firing, the forward momentum change in the spaceship plus the backward momentum of the gases ejected add up to zero as required by the law of conservation of momentum. Interactions between the spaceship ...
December 16, 2008

science
Liquid soap is a viscous (thick) solution that can form a solid by the evaporation of water in it. Some liquid soap remains at the tip through capillary action and forms a solid deposit by the evaporation of water. Initially, the spout opening becomes narrower and eventually ...
December 16, 2008

Chemistry
Based on your description: 3) 55º-5º = 50º 5) (4.18J/g.ºC)(100.0g)(50º) = 20900 J 6) 20900J/75g = 278.7J/g 7) (278.7J/g)(18.0g/mol) = 5016 J/mole = 5.016 kJ/mol 8) %Error = (6.02-5.02)(100)/6.02 = 17% ---------- NOTE: Some of the heat lost by the warm...
December 15, 2008

chemistry
1. F = 4.0, O = 3.5, N=3.0, and Cl = 3.0 2. Any element in Group IVA (Group #6) of the Periodic Table. 3. Any element in Group VIIA (Group #9) on the Periodic table.
December 15, 2008

Chemistry
Not many elements can be identified by the flame color. The most common ones are: Pinkish violet -- K Very bright yellow orange -- Na Red -- Li or Sr (different shades of red) Pale green -- Ba Bright green -- Cu Orange -- Ca, Mg, and other elements
December 15, 2008

Chemistry
3-methylcyclohexane is an incorrect name. Could it be 3-methylcyclohexene?
December 13, 2008

chemistry
That sounds like a proverb, not a clear statement of fact. Both, water and salt are widespread in nature. They are together in sea water. Dried up seas are the origin of huge underground salt deposits. The statement you are quoting is cute but its meaning is too vague to ...
December 12, 2008

Chemistry
Convert the grams to moles by dividing the grams by the formula mass. Multiply the number of moles by 22.4 L/mol.
December 11, 2008

college-Organic Chemistry
Its reactivity (instability) may not be high enough to be classified as anti-aromatic. [Actual data on this are not easily available.]
December 11, 2008

chemistry
Fruits and vegetables are easier to preserve cooked since microbial and enzyme actions are slowed down or stopped. Some vitamins and other nutrients may be reduced or destroyed by cooking.
December 11, 2008

Grade 11 Chemistry!
This question can't be answered exactly without knowing the density of q 10%(m/m) solution. That density based on the table at: http://www.chembuddy.com/?left=CASC&right=density_tables is 1.1111 g/ml. Use this density to find the mass of 250 mls. (a) Calculate the mass of ...
December 10, 2008

CHEMISTRY HELP
Why two postings of the same question? You have an answer at: http://www.jiskha.com/display.cgi?id=1228951921
December 10, 2008

9th grade chemistry
The formula of the compound form from Pb^2+ and NO3^-1 ions is Pb(NO3)2. To answer the question,find the formula masses of Pb(NO3)2 and (NO3) times 2 . grams Pb(NO3)2 = [Pb(NO3)2 / (NO3)(2)](55.6g)
December 10, 2008

chemistry
Not sure what you are asking but ... electrons in inner shells reduce the attraction between the (positive) nucleus and outer electron shells.
December 10, 2008

Chemistry
What procedure did you follow? To get recrystallization you must saturate (or nearly saturate) a solution at a high temperature, then let is cool down to a lower temperature. You get the most recrystallization if the solubility at high temperature is much higher than at low ...
December 9, 2008

Chemistry
The charge of a large ion is less concentrated because of its larger radius and surface area. That makes the attraction between Ca^2+ and S^2- ions weaker than the attraction between the smaller Mg^2+ and O^2- ions.
December 7, 2008

physics
Let: m = a small mass M = mass of the earth r = distance from the center of mass m to the earth's center. Constants: G = 6.67x10^-11 m^3/kg.s^2. M = 5.98x10^24 kg R = 6.38x10^6 m (Earth's radius) Law Of Gravitation: F = GmM/r^2 F = m(GM/r^2) = mg GM/r^2 = 3.00 m/s^2 ...
December 6, 2008

Chemistry
Your method is correct but your power of 10 is wrong.
December 6, 2008

Chemistry
Bond angles are more important in building molecular models than bond lengths. You can get approximate bond lengths by looking up the covalent radius of both elements linked and add them up. Double and triple bonds are shorter than single bonds. Some of the bonds you need are ...
December 5, 2008

Chemistry
Probable names: [Al(H2O)6] Br3 Aluminum hexaaquo bromide [Cr(NH3)6] Cl3 Chromium hexammine chloride(III) K3[FeF6] = Potassium hexafluoroferrate (III) [Zn(OH)4]-2 = Thetrahydroxy zincate (anion)
December 4, 2008

Chemistry. Please help!
Sorry. The 3rd one looks OK.
December 3, 2008

Chemistry. Please help!
It looks OK. For the 2nd question convert the grams of CO2 to moles and use the Ideal Gas Law to find the pressure due to CO2.
December 3, 2008

Science, Chemistry
After looking at your question more carefully, I changed my mind. The equation, V1C1 = V2C2, works only if the concentrations are ratios of amount of solute over volume of solution. The formula you are using is new to me and since you have made substitutions into it I am not ...
December 3, 2008

Science, Chemistry
Use the equation: V1C1 = V2C2 (V1)((0.96) = (1000mls)(0.70) Solve for V1
December 3, 2008

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