Friday
August 1, 2014

Posts by GK


Total # Posts: 644

Chemistry
ΔE = q - w ΔE is the change in internal energy of a system q is the heat flowing into the system w is the work being done by the system The 2424 J is released to the surroundings. It should be assigned a negative sign. The 6 KJ is work done against the surroundings. ...

Chemistry
According to the Work-Energy Theorem, Work = Ek(final) - Ek(initilal) Ek(initilal) = (1/2)mv^2 = (1/2)(0.17kg)(4.5 m/s)^2 Ek(final) = (1/2)mv^2 = (1/2)(0.17kg)(4.0 m/s)^2 Work = ?__________ NOTE: This looks like a Physics question.

Chemistry
This looks like diatomic species (molecules or ions) of third row elements with 14 electrons. It may be Cl2, SCl-, etc. You should be able to come up with a couple more.

chemistry
Distinguish experimentally? 1-octene would discolor a solution of Br2. 1-octanol and toluene would not react with Br2 easily. 1-octanol could be oxidized easily by a chromic acid solution or other strong oxidizer. One of the reaction products would be Cr^+3 ions. 1-octene and ...

Chemistry
Not arguing with DrBob. Just presenting another way of looking at it using change in oxidation numbers as the yardstick for electrons transfer. The balanced reaction is: 2C3H7OH + 9O2 --> 6CO2 + 8H2O Each of the 18 oxygen atoms in O2 changes from an oxidation state of 0 to ...

chemistry
You need to describe your model in more detail. Chemical equilibrium is the result of two opposite processes occurring e same rate. Does your model show that?

chemistry
The reaction between the added solid and NaOH is: NaH2PO4 + NaOH --> Na2HPO4 + H2O 10.0gNaH2PO4 /120.0g/mol = 0.0833 moles NaH2PO4 initially. In the rection, the limiting reactant is NaOH. (0.150 L)(0.20 mol/L) = 0.030 mol NaOH 0.030 moles of NaOH ---> 0.030 moles Na2HPO...

Chemistry
You can have three different chemical equations going on at the same time: C5H12 + 8O2 ==> 5CO2 + 6H2O 2C5H12 + 11 O2 ==> 10CO + 12H2O C5H12 + 3O2 ==> 5C + 6H2O The relative amounts of C5H12 undergoing each reaction simultaneously varies depending on the availability ...

chemistry
The length of a carbon chain has more to do with melting and boiling points than the number of bonds. Double bonds tend to lower the melting point if the chain is in a "cis-" configuration. As BobPursley pointed out, the question is not clear enough for a definite a...

Chemistry
See both answers given to the question below: http://www.jiskha.com/display.cgi?id=1254688201

Chemistry
The question is to find grams of CaH2. The balanced chemical equation is: CaH2 + 2H2O --> Ca(OH)2 + 2H2 This mole ratio must be taken into account. Find the moles of H2 as DrBob showed you, then multiply by 1/2 to get moles of CaH2. Finally convert moles of CaH2 to grams.

chemistry
The six orbitals on the central atom, As, are sp^3d^2 hybrids. That is the kind of hybridization you have in an octahedral structure, "XY6". Each of the hybrid orbitals on the As atom is forming a sigma bond with the half filled p orbital on an F atom.

chemistry7656847547659756946534
HCl is a molecular compound with relatively weak intermolecular attractions. It is a gas at room temperature. NaCl is an ionic solid because of the strong ionic attraction between the Na+ and Cl- ions. The physical properties (state at room temperature, melting and boiling poi...

chemistry
If you wanted to know what amount of sodium chloride was delivered into another container, you would weigh the vial with the salt in it, then weigh the "empty" container which may have traces of salt stuck in it.

Biology/Chemistry
You will find your answer here: (Broken Link Removed)

chemistry
Here is a quick rundown of the way I think it should be done: If the weight is 4590 N, m = W/g, or m = 4590 N / 9.8 kg/N = 468.4 kg d = 468.4 kg / 0.500 m^3 = 937 kg/m^3 1 m^3 = 1000 dm^3 0.500 m^3 = 500 dm^3 d = 468.4 kg / 500 dm^3 = 0.937 kg/dm^3 It can be shown that a densi...

chemistry
To continue or add on to DrBob's explanation, hydrogen bonding due to O-H groups is stronger than hydrogen bonding involving N-H groups. That is probably related to the electronegativity differences mentioned by DrBob.Hydrogen bonding is the main intermolecular force in bo...

Chemistry
It depends on what the material is. If you know the density in grams/milliliter, the number of grams for 1 mL is numerically equal to the density.

chemistry
Start with the Ideal Gas Law PV = nRT or n = PV / RT K = n/P (from Henry's Law) n/P = V/RT (from the Ideal Gas Law) or K = V/RT (by combining the last two equations) (V = liters, R = 0.0821 L.atm/K.mol, T = 298K) Substitute to get the constant, K

Chemistry130
As you go down a column (group, family) on the periodic table, the number of electron shells increases "shielding" the nucleus and weakening its attraction on outer (valence) electrons. As you go from left to right on a row (period), the nuclear charge increases but ...

Chemistry
NO2, the compound is nitrogen dioxide. NO2^-, is the nitrite ion.

Chemistry - pH
a) 0.35M HCl (monoprotic strong acid) produces a 0.35M [H+] solution. pH = -log(0.35) c) 0.35M NaOH (strong base) acid produces a 0.35M [OH-] solution. pOH = -log(0.35) pH = 14-pOH b) 0.35M HC2H3O2 (WEAK ACID) does not dissociate completely. Its Ka = 1.8x10^-5 [H+] = sqrt[(Ka)...

chemistry
"Metal" generally refers to a metallic element such as iron, copper, silver, etc. An "alloy" is a homogeneous mixture of two or more metallic elements. Examples, Brass (copper+zinc), stainless steel (iron+nickel+chromium), 14K gold (gold+copper), etc.

chemistry
You should know or look up: 1 nm = 1x10^-9 m 1 cm = 1x10^-2 m Using the above: (294nm)(1x10^-9 m/nm) = ?___m (?---m)(1 cm/1x10^-2m)

Chemistry
Look up the atomic masses of Pb, P, and O Multiply the atomic mass of Pb by 3. Multiply the atomic mass of P by 2. Multiply the atomic mass of O by 8. Add the three values you got. That is the formula mass which you label "grams/mole".

Chemistry
1 mole = 6.02x10^23 A bromine molecule has the formula Br2. Multiply the number of Br2 molecules by 2 to get the number of atoms of bromine. Divide the number of atoms by 6.02x10^23 atoms/mole to get moles of Br atoms

chemistry
A sodium carbonate, Na2CO3, solution would neutralize ethanoic acid forming sodium acetate in the aqueous layer. A calcium chloride solution, CaCl2, would mix with the ethanol in the aqueous layer. Most of the ester would be in a separate layer on top of the water layer. The l...

chemistry
Here an outline of the solution. The answers to the answers in each step should have at least four significant figure. 1. Convert the grams of CO2 and H2O to moles 2. Moles of carbon, C, equals the number of moles of CO2. Convert the moles of C to grams of C. 3. Moles of hydro...

Chemistry
mass = density x density or M = DV Applying this to water, 36.84g = (0.9970g/mL)(V) For chloroform, 41.43g = (x)(V) Dividing the left sides and right sides, we get: 41.43g / 36.84g = (0.9970g/mL) / x (the equal volumes cancel out) Solve the above proportion for x

college biology
A sample containing starch will cause an iodine solution to turn dark blue. A sample containing fats will leave a greasy stain on paper. Simple sugars can be tested with Benedict or with Fehling solutions. The blue color of the test solution will change from yellow to red. Pro...

Chemistry
Polysaccharides and disaccharides must be digested to monosaccharides before being absorbed into the bloodstream.

Chemistry II
The general word is solvation. If the solvent is water, it could be called hydration.

chemistry
I think the question is intended for %H by mass: Using atomic masses and subscripts in C7H8, %H = (100)(8)(1.00794)/[(7)(12.011)(8)+(8)(1.00794)] %H = 8.75% by mass

CHEMISTRY
1. Look up the heat of vaporization of isopropyl alcohol. The figure I found is 44.0 kJ/mole. Divide that by the molar mass to get the kJ/g. Multiply by 1.01g to get the heat absorbed from the aluminum block. 2. The applicable formula for the aluminum is: heat = (specific heat...

chemistry
In a six-carbon chain, there are 5 C-C bonds. When those bonds break during combustion, energy is absorbed, not released. The energy released is due to the formation of C=O bonds in CO2 and H-O bonds in H2O. Calculating the NET energy released must take into account the energy...

Chemistry
Diamond tips are used because they are harder than most materials we would drill into. Diamond is the hardest material, with the possible exception of some forms of boron nitride.

Chemistry
*10 moles of Na2SO4 is 3*10=30 moles of particles. *Convert 0.500 kg H2O to moles. *Total moles = 30 + moles of H2O *Mole fraction of H2O = X(H2O) = (moles H2O) / Total moles. *Look up the vapor pressure of H2O at 30ºC = P(H2O) *Vapor pressure of solution = [X(H2O)]*[P(H...

chemistry
There IS, the cubic meter, m^3. The basic SI units in the "MKS" system are the meter, the kilogram, and the second. Derived units such as those for volume, velocity, force, energy, etc, are "SI" as long as they are based on the basic SI units. Example: The ...

Chemistry
It could a number of things only known to your teacher and/or the author of the printed instructions for the lab. It sounds like an experiment to determine the density of a material. When you measure the mass and the volume of an object, you have the data needed to calculate i...

Chemistry
1. We identify substances from their physical and chemical properties. 2. If we know the density of a substance, we can calculate the mass of a sample from the volume or the volume from the mass. 3. The density of a substance is taken into account in determining how that subst...

Biochemistry
500.00g / 89 g/mol = 5.62 moles 1 mole = 1000 millimoles (5.62 moles)(1000 mmol/mole) 5620 millimoles. Are you sure the mass is 500.0 grams? Could it me milligrams?

Chemistry
Moles of Ti = 3.0g / 47.87g/mol = 0.0627 moles Ti 8.0g Cl2 / 70.9g/mol = 0.113 mol Cl2 Available ratio: (0.113 mol Cl2) / (0.0627 moles Ti) = 1.80 mol Cl2 / 1mole Ti Needed Ratio: The Cl2 / Ti mole ratio in the balanced chemical equation = 2 mol Cl2 / 1 mol Ti The comparison ...

Chemistry
The reaction is: C7H8 + Br2 --> C7H7Br + HBr Find the molar masses of C7H8 and of C7H7Br The theoretical yield is: (1.5g C7H8)(mol.mass C7H7Br / mol.mass C7H8)

chemistry
Unsaturated fats (oils) contain one or more double bonds that are chemically active. That makes them vulnerable to oxidation and to breaking of the long fatty acid chain at the double bond into shorter fatty acid chains. What does this tell you about the relative stability of ...

Chemistry!
1. Yes 2. Yes

CHEMISTRY
According to the Law of Conservation of Mass, the total mass before and after a physical or chemical change remains the same.

chemistryy
Bond breaking is an energy absorbing process. The question should read: "What is the amount of energy absorbed when a carbon carbon single bond is broken?" In a spontaneous decomposition, energy is released because of the formation of new, more stable bonds.

chemistry
The melting point of PbCl2 is about 501 deg C. If the crystals melted, that would account for the increased conductivity. Impurities in the crystals could have lowered the melting point to 500 deg C. easily.

chemistry
Here are some online articles on ozone and ozone de[pletion: http://www.biospherical.com/nsf/student/page2.html http://www.ucar.edu/learn/1_6_1.htm (Broken Link Removed) (Broken Link Removed) http://www.atmosphere.mpg.de/enid/208.html

Chemistry
The reaction is: HCl + NaOH --> NaCl + H2O For 100% neutralization, moles NaOH needed is 3.75. For 50% neutralization, you use half of 3.75 millimoles NaOH. At that point, 50% of the HCl is still there. [H+] = conc. of HCl = (moles HCl)/(Total volume)* *Note: Total volume (...

Chemistry
Ka = [H3O^+][C3H5O3^- ] / [HC3H5O3] Let [H3O^+] = [C3H5O3^- ] = x Ka = [x][x ] / [conc. - x] (exact) Ka = [x][x ] / [conc.] (approximate if x is much smaller than cocnetration) I assume conc. = 0.0284 is moles/liter [H3O^+] = [C3H5O3^- ] = (0.067)(0.0284) Ka = {[(0.067)(0.0284...

Chemistry
pH + pOH = 14 pOH = 14-10.08 = 3.92 [OH-]=-log^-1(3.92)=1.2002x10^-4 --------- Kb = [BH+][OH-] / [B], with B = base here, Kb = [C17H21O4NH+][OH-] / [C17H21O4N] since [C17H21O4NH+]=[OH-] Kb = [OH-]^2 / {[C17H21O4N]-[OH-]} Since [OH-] is much smaller than the overall concentrati...

chemistry
Here are the initial steps of the solution DrBob suggested: Let V = liters of solution. moles of H+ with pH 6 is = 1.00x10^-6)(V) The total moles of H+ in the mixture is: moles H+ = (1.00x10^-6)(V)+(1.00x10^-7)(V) [H+] = (moles H+)/V

Chemistry
I think bobpursley meant that: pOH = -log[OH-] and pH = 14 - pOH Use these relationships to get the pH after finding the molarity of KOH = [OH-] as bobpursley suggested.

chemistry
Relevant conversion facts: 1 mL = 0.001 L --> 1.00x10^-3 L 1 microliter = 0.000001 L --> 1.00x10^-6 L We multiply the measurement we want to change times the appropriate labeled conversion factors. After you do units cancellations and numerical calculations, you end up w...

Chemistry
I hope the question refers to a particular decomposition. Some decompositions are very exothermic and/or exergonic. The explosive decomposition of nitroglycerin and TNT are examples of that. The same applies to synthesis reactions. Not all of them are exothermic.

Chemistry
Let HA = benzoic acid ----------- moles NaOH(initial) = (0.015L)(0.50 mol/L) = 0.0075 mole moles HA(initial) = (0.0300L)(0.50 mol/L) = 0.015 mol OH^- + HA --> H2O + A- moles of A- formed = 0.0075 (same as initial OH-) moles HA remaining = 0.0150- 0.0075 =0.0075 mol [A-] = m...

College Chemistry
Use the Ideal Gas Law to get the moles, n, or propane: PV=nRT Convert the 150 PSI to atm (1 atm = 14.7 psi) Convert deg C to deg K (K = C + 273) R = 0.0821 L.atm/K.mol Substitute and solve for n (moles) ---------- Convert the moles to grams (1 mole C3H8 = 44.09g) Convert the g...

College Chemistry
Use the Combined Gas Law: P1V1 / T1 = P2V2 / T2 P1 = 1.0 atm, V1 = 0.50L, T1 = 25+273=298K P2 = ?____, V2 = ?____ (both given) Solve for T2 to get the temperature in degrees Kelvin

Chemistry
The statement is false, You got a perfect explanation from DrBob. Here is a less formal explanation based on the equation for deltaG: Chemical and physical changes happen because of two universal trends: A. A trend toward lower energy. This favors exothermic reactions as far a...

chemistry
In simple monoatomic (1 atom) ions like Al^3+, Ba^2+, S^2-, etc., the oxidation number is the same as the electrical charge.

chemistry
Elements in Group 1 are assigned an oxidation number of 1. That is the same as the electrical charge on ions formed frm that group. Elements in Group 17 (or Group VII-A) form ions with an electrical charge of -1. That is also their oxidation number in BINARY compounds like NaC...

Chemistry
The total electrical charge on the left side of a chemical equation must be equal to the total electrical charge on the right side. That is not the case on either chemical equation as you typed it.

Chemistry
The two chemical equations are balanced for electrical charge and number of atoms. One additional requirement is that they actually occur. That is a little more difficult to ascertain.

Chemistry
Find the moles of HBr = (liters)(M) Find the moles of KOH = (liters(M) If moles of HBr = moles KOH, pH = 7 If moles of HBr is larger than moles KOH, the mixture is acid and [H+] = [(moles HBr)-(moles KOH)]/(total liters) pH = -log[H+] If moles of KOH is larger than moles of HB...

Chemistry
The equilibrium in both mixtures is: HC2H3O2(aq) <=> H+(aq) + C2H3O2^-(aq) For the first mixture use the Henderson-Hasselbalch Equation to get the pH: pH = pKa + log{[C2H3O2^-]/[HC2H3O2]} NOTE: [C2H3O2^-] = molarity of NaC2H3O2 pH = pKa + log{1} In the second mixture, re...

chemistry
Each metal ion in the question is surrounded by six H2O molecules forming Hexaaquo complexes. The link below gives a detailed description of the reactions between the original aquo complex and NH3 for several ions, including Al(H2O)6^3+, Fe(H2O)6^3+, and Mn(H2O)6^2+: http://ww...

chemistry
The definition of pH is: pH=-log[H3O+] An equivalent statement is: [H3O+] = 10^-pH The hydronium concentration is the antilog of the (-pH) For this example, [H3O+] = 10^-10.5 = ?? The definition acid, basic, and neutral pH's should be something you can look up in your text...

chemistry
Something to consider in handling of units: 1.00 g/mL = 1 g / 1 mL 1 g / 1 mL = 1000g / 1000mL = 1 kg / L The above steps show that a density of 4.5 g/mL is equivalent to 4.5 kg/L. Using a density of 4.5 kg/L should make it possible to get the volume in directly in liters wit...

Chemistry
DrBob mentioned gunpowder and mixtures which include ammonium nitrate. Other important explosives are nitroglycerin (dynamite) and trinitrotoluene (TNT) which are formed by the action of HNO3 on organic compounds like glycerol and toluene.

Chemistry
DrBob answered the question the way most of us would. A little added information here: Corrosive to most people means an oxidizing agent. It causes the oxidation (rise in oxidation number) of other elements, especially metals. More metals dissolve in HNO3 that they do in the o...

Chemistry
Based on the evidence included in the question, cohesive forces (attraction between particles within a material) decrease: Hg > H2O > naphtha. Next, consider how the boiling point is related to cohesive forces and deduce whether the boiling points compare in the same way...

Chemistry
The web page DrBob referred to gets into the relationship between a definite mass ratio and a definite particle ratio. The particle model of matter becomes the explanation of the definite mass ratio. A less profound but accurate answer might be to merely write the chemical equ...

Chemistry
Your URL is not properly typed. It should have been: http://img242.imageshack.us/img242/933/picture2jt7.png (Typed, not pasted. Your URL has spaces and carriage returns that should not be there) The high priority groups on the 2nd formula are: C3H5Cl2 on the left side of the d...

Chemistry
The image location is not given properly

Chemistry
Same response as before. You are not giving the web location properly.

Chemistry
Neither URL gives the location of the web page. The code you provide looks like a folder and an image file in it. Not enough.

chemistry
Cd3(PO4)2

chemistry
0.50 mLs of KH2PO4 was diluted to 100 mLs in the volumetric flask. The concentration of the diluted KH2PO4 in the 100.00 mL volumetric flask is: (0.50mLs /100mLs)(Original concentration of KH2PO4). Not sure where the decimal point is in the original phosphate concentration.

Bio-Chemistry
This looks like a poll. I vote for digestion. Well, [destructive] metabolism would work also. Study the assigned materials and let them be your guide.

Dr.Bob - Question
For a chemistry major, a good college chemistry curriculum should be consistent with recommendations of the American Chemistry Society (ACS). Here is one of them to look at: http://tars.rollins.edu/chemistry/Courses/ACS_Major.shtml If you do not have a chemistry major already ...

Dr.Bob - Question
Christina, when it comes to choosing a major (that comes before choosing a specialized area within a major), the question is not "what do I want to be?" but "what do I enjoy doing?". My suggestion would be to simply major in chemistry. That is all you can r...

chemistry
There are two question in this problem: a) Find "q" for the sample burned. b) find "q" for 1.25 moles of C6H6. Your numerical answer for the first part is correct but you are not paying attention to unit labels. It is mislabeled. For the second part, to fin...

Chemistry
Stability of the carbocation increases with the number of alkyl groups linked to the charge-bearing carbon. Tertiary carbocations are the most stable.

Chemistry
Vinyl Chloride, H2C=CHCl would be the simplest compound in this group. Any one of the H's can be replaced by an alkyl group to form a more complicated vinyl organohalide. Vinyl molecules (monomers) can link together to form polyvinyl chloride plastics (PVC). A simple test ...

Chemistry
Comment of Part C: Normally the effective molality when we have two solutes would be the SUM of the two molalities: m(effective) = m(A) + m(B) However since A and B combine to form C, if we use equal moles of the two solutes, the effective molality will be equal to the molalit...

Chemistry
a) The freezing point will decrease the most (compared to parts "b" and "c". If the molality of the solute is m, the lowering of the freezing point will be deltaT = 2•Kf•m (the effective molality is 2m) b) The lowering of the freezing point will b...

chemistry
The basic relationships above are: 1. Heat transferred = (heat capacity)(temperature change), or deltaH = C•(T2-T1) ( T1, T2 = initial and final temperatures ) 2. Heat lost by B = Heat gained by A

chemistry
Let the heat capacity of A = c. The heat capacity of B is 2c. Let the final temperature be T. The heat lost by B when A and Be are placed together is: (2c)(450-T) The heat gained by A is (c)(T-300). Assuming the Law of conservation of Energy holds, and there are no heat losses...

Chemistry
DrBob's suggestion is very good. If you do not have easy access to a lab, here is a clue: • Cu(H2O)4^2+ ions dominate at low CuBr2 concentrations and they are blue. • CuBr4^2- ion concentrations appear at high Br- ion concentrations and their color is green.

chemistry
0.106g / 0.00183 mol = 57.9 g/mol [Acetone = CH3-CO-CH3, mol. mass about 58] Not bad!

chemistry
If the question is about making predictions when a metal is placed in a solution of a salt of another metal, the rule is: a metal (in its elementary form) will replace any other metal in a salt, if the first one is higher than the second on the metal activity series: (Broken L...

chemistry
If this is a lab question, the answer should come from what you observed. The experimental setting is a zinc metal strip placed in a solution of lead nitrate. IF a reaction occurred, the zinc strip will lose some of its mass and its surface will become dull and covered with a...

chemistry
Now I am beginning to worry. I missed the units given. Could it be grams/minute instead of g/L?

chemistry
The rate of effusion is inversely proportional to the square root of the molecular mass. Let the rates be Ra, Rb. Let the densities be Da, Db Da / Db = 1/1.2 Based on the Law of effusion, Ra/Rb = sqrt(Db) / sqrt(Da). Db/Da = sqrt(1.2)/sqrt(1) (3.41g/L) / Rb = sqrt(1/1.2) (3.41...

chemistry
That water depth of 20.5 m looks incredible. The 80.7 cm^3 is not connected to anything. It would be pointless to get started on long answer to a question that seems to need some checking and editing.

chemistry
1) Change 100.0g C2H2 to moles (n) 2) Calculate the ideal pressure using the Ideal Gas Law: PV = nRT, P = nRT/V 3) Calculate the real pressure using the Van der Waals Equation. You can find the equation here: http://hyperphysics.phy-astr.gsu.edu/Hbase/Kinetic/waal.html Constan...

organic chemistry
Sorry, my clue to the second question needs correction: 2. CH3S^- would react most readily with the haloalkane that forms the MOST stable carbonium (R+) ion. Inversely, a primary haloalkane with the shortest carbon chain would be the least likely to react.

organic chemistry
Here are a couple of clues (not answers): 1. One of the choices involves a Br atom bonded to a secondary carbon atom (one attached to two other carbon atoms). This is the one that forms the more stable carbonium ion, and the weakest C-Br bond. 2. CH3S^- would react most readil...

Chemistry
Ag3PO4(s) <=> 3Ag^+(aq) + PO4^3+(aq) Ksp = [Ag^+]^3•[PO4^3+] Let [PO4^3+] = s then [Ag^+]= 3s = 4.5 x 10^-4 mol/L. s = 1.5x10^-4 Ksp = (3s)^3•(s) = 27s^4 substitute the value of s and solve

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