Friday

February 24, 2017
Total # Posts: 72

**MATH**

How could you find out which weighs more, one ton of pillows or one ton of bowling balls?

*March 31, 2015*

**reading and writing**

A The answer is a

*March 31, 2015*

**MATH**

David took a survey of 12 people to find out what their favorite animal is. Of those, ⅓ of the people said they liked dogs best. How can you find out him many people liked dogs best?

*March 31, 2015*

**Math**

Between 6 A.M and 10 A.M the temperature rose by 5F. Between 10 A.M and 2 P.M the temperature rose by 6F. Between 2 P.M and 6 P.M the temperature rose by 0C. Would you be able to tell how much the temperature rose since 6 A.M? Why or why not?

*March 31, 2015*

**chemistry**

I am trying to calculate geometry optimization of cyclodextrin, however, the computer always show error 2070 in gaussian. I used sem-empirical pm3 and try pm6, and tried to find any method to do this work, but every try could not work. I hope any body on Jiskha can give me ...

*May 28, 2012*

**physical chemistry**

the aprroximate method to solve the shrodringer equation for hydrogen like atom? Please help, thank

*June 4, 2011*

**inorg, chem**

please help me to solve it, thank you so much in advance: propose organic compounds that are isolable with 1. Mn(CO)5(CpCo)(CpCo)C(Co(CO)4)3 2. Cr(CO)4(ì-PH)Cp*Mn(CO)

*March 15, 2011*

**Algebra**

-3x + 2y = 8 x + 4y = -4 use substitution method to solve the linear system.

*February 22, 2011*

**phy. chem**

start from the Maxwell-Boltzmann distribution and derive an expression for the most probable speed of a gas of molecules at a temperature T. Go on t demonstrate the validity of the equipartition conclusion that the average translational kinetic energy of molecules free to move...

*January 23, 2011*

**chemistry, Please help.**

Please tell me where I can find the articles ( free) to represent the Setvens rearrangement and Favorskii rearrangement. I have to have them for presentation but I have not taughed about these reaarangenment yet. I hope somebody on Jiskha will help me to find it. I really ...

*November 9, 2010*

**Math**

This is so easy and I'm a fourth grader. All you have to do TJ is to multiply 78 by 21

*October 14, 2010*

**chem**

Ionic bonds and covalent bonds, which one is the stronger. My present teacher said that covalent bond is the strongest one. I learned ionic interaction is the strongest and many chem. books say so. Now i am confused. Is my present teacher right. Please explain this for me, and...

*October 5, 2010*

**chemistry**

mol Na2S = (0.01mol/L)*2.00ml*1L/1000mL = 0.002mol mol Hg(NO3)2 = 50.0ml*(0.0005mol/L)*1L/1000mL = 0.000025=2.5*10^-5 Hg(NO3)2 limiting reagent max mass of precipitate = 2.5*10^-5 * molar mass of Hg(NO3)2

*August 13, 2010*

**chem**

why we have to normalize the proton NMR areas to determine the mole % oa a compound in a mixture?

*May 31, 2010*

**Chemistry**

4.6*10^-3 = [NO2]^2/[N2O4] => [NO2] =3.48*10^-1

*May 31, 2010*

**Chemisty**

MnO4- +5e -> Mn2+}*2 C+1 -2e -> C+3 }*5 2MnO4- + 5C6H7O +6H+ -> 2Mn2+ + 5C6H7O2 + 3H2O Step 1: realize the oxidation of element: (oxidation of H and O not change) write half reaction equalize the number of election yieled and accepted by the coefficient ( here e yield...

*May 31, 2010*

**physics**

1.calculate the commutators a/ [x^2,p^2] b/ [a,a^+n] I don't know how to solve it. Please help. I really appreciate.

*March 12, 2010*

**calculus**

as t-->0, we have 8t-->0, so lim (sin(8t))^2/t^2 = [lim sin(8t)/t].[limsin(8t)/t] as8t-->0 =8.[limsin(8t)/8t].8[limsin(8t)/8t], 8t-->0 = 8*1*8*1= 64 you know the formula lim (sint/t)=1 as t-->1, aren't you?

*March 6, 2010*

**calculus**

y' = (3-secx)'tanx -(3-secx)(tanx)'/(tanx)^2 = -secx(tanx)^2 - (3-secx)secx/(tanx)^2 = -secx[(tanx)^2 + (3-secx)]/tan^2x =-[(tan)^2 +3 -secx]/sinx

*March 6, 2010*

**chemistry**

Br is larger than Cl,yet the two atoms have identical axial destabilization energies. Why?

*March 6, 2010*

**Algebra**

let y=0, --> x= 6/5=1.2 let x=0 --> y = 6/3 = 2

*March 6, 2010*

**Algebra**

They are correct b) (1.2,0) and(0,20

*March 6, 2010*

**chemistry**

deltaG = -RTlnK R=8.314J/mol.K you got R, T so K found by that formula.

*March 6, 2010*

**chem**

What is the chemical formula of fertilizer 13-13-13. Pleas tell me. Thanks a lot

*February 7, 2010*

**chem**

how many milliter of .246 M HNO3 should be added to 213 ml of 0.00666 M 2,2'-bipyridine to give a pH of 4.19? please help, does this problem need to be solved with ka or kb?. Is 2,2'- bipyridine a base, this is the problem from my text book, but it is not given by the ...

*February 2, 2010*

**phys**

show [f(xop), d/dx] = -df/dx please help, can sb gives a hint? I really appreciate.

*January 28, 2010*

**phys**

1) Pf(x)= f(-x), p operator Find the eigenvalues and eigenfunction of p 2)Show [f(xop), d/dx] = - df/dx

*January 28, 2010*

**CHEM**

increasing atomic radius: oxygen<carbon<aluminum<potasium

*January 24, 2010*

**CHEM**

neon<oxygen<sulfur<aluminum

*January 24, 2010*

**chemistry**

ionization energy is the minimum energy (Kj/mol)required to remove an wlectron from a gaseous atom in its ground state. affinity energy: the negative of the energy change that occurs when an electron is accepted by an atom in the gaseous state to form an anion

*January 24, 2010*

**chem**

Electronegativity of fluorine is the highest among the chemical element(its electronegativity = 4),so F tends to receive electron, not yield. Therefore, fluorine has the higher ionization energy than iodine.

*January 24, 2010*

**chem**

the properties of elements are based on the valence electron, the elements in the same family generally have similar properties because they have the same number of valence electron.

*January 24, 2010*

**chem**

Species of arsenic found in kriking water include (AsO3)3-, (CH3)2(AsO2)2-, (CH3)AsO3 2-, and (AsO4)3-. Pure water containing no arsenic was spiked with 0.40microgram arsenate/L. Seven replicate determinations gave 0.39, 0.40, 0.38, 0.41, 0.36, 0.35 and 0.39 mcrogram /L. Find ...

*January 24, 2010*

**chemistry**

6.2(+_ 0.2) - 4.1 (+_ 0.1 ) + ? [6.2( +_ 0.2) - 4.1(+_ 0.1)] : 9.43(+_0.05) find absolut uncertainty and relative uncertainty. PLEASE HELP:I solved them and got the exact absolute uncertainty like the answer key, but I didn't get right answer of relative unsertainty, my ...

*January 18, 2010*

**chemistry**

Why do the molecules that have the structures such as H2C=C=CH2 or HO-CH=CH2 are unstable?

*January 13, 2010*

**phys**

i solved D~11.7*10^-2, but the answer key is .0956

*January 6, 2010*

**phys**

Is D~11.7*10^-2

*January 6, 2010*

**phys**

What is the minimum lens size (in meters) that will permit just resolving 2 stars 1.1 second apart using light of 510nm?

*January 6, 2010*

**MATH**

Let x be the orders Harry sold y be the orders McDonal sold x + y = 60 (1) and y/x = 3 (2) s0lve this system x =15, y =45 after increase H. sold 15+15 =30 Mc. sold 15*6 + 45 = 135

*December 30, 2009*

**chemistry**

Thank you so much drwls

*December 29, 2009*

**chemistry**

Thank you drwls i am reviewing my chemistry and doing the problems from my textbook. Because my teacher did not have the lecture about this part, so I am reading my text book and trying to solve problems. My textbook only have two problems of this theory: 1/ find how many ...

*December 29, 2009*

**chemistry**

1. The mass spectrum can be observed for all forms: pos. ion, neg.ion, molecules, and atoms, can't it? 2. Is there a formular to calculate how many spectrum of the substances we need to observe? Please give me some examples, and calculation. 3. I knew the examples of H2S...

*December 29, 2009*

**Chemistry**

Ho is the element of the Lanthanide series, the Lanthanides have the electrons are arranged into the orbital 4f.If you start from the element La (Z= 57), write the electron configuration of La,Ce(Z= 58),..., to Ho(Z=67) , you will understand why Ho=[Xe]4f11 6s2, it cannot 6s2...

*December 27, 2009*

**Chemistry**

5f^14 and 5f^7 is stable ( 5f^7 : all spin is up), so you cannot drive 5f^8 instead of 5f^7 6d^1

*December 27, 2009*

**math**

-4y = -3x +4 divide by -4 -4y/-4 = (-3/-4)x + 4/-4 y = (3/4)x -1 the slope is 3/4 and the y intercept is -1

*December 27, 2009*

**Chemistry**

Yes

*December 23, 2009*

**Algebra**

(AB^2)/C - B^2 = (B^2)(A/C) -B^2(1) = B^2( A/C -1)

*December 23, 2009*

**Pre Cal**

cos^2 + sin^2 =1 cos^2 = 1-16/25 =9/25 sin theta terminates in quadrant II, so sin>0 but cos <0 therefore cos =-3/5

*December 23, 2009*

**Math**

there are 7 times Sean and Kevin have the probability to be selected as partners.

*December 15, 2009*

**math**

let the number be x so (x+8)(-4)-5=10 -4x-32-5=10 -4x=47 x=-47/4

*December 15, 2009*

**science**

It is not a homework, it is my question, and I hope it is explained. Sometimes at night I look ATTENTIONALLY at the starry sky , notice and see that there is an object which is as small as a star is moving. It is very very far and has the light as the light of a star, and I ...

*December 15, 2009*

**Math**

sure, you can say $1.70

*December 15, 2009*

**Math**

85/5.95= 14.28 so se can buy 14 cd the change = 8500-590*14= 170 cents

*December 15, 2009*

**phys**

Thanh you drwls

*December 15, 2009*

**phys**

It is not a homework,but this is my question and I hope sb to explain it for me: There is not snow is the area I am living, but in the winter, sometimes I see the ice on my car. I notice that the water is ALWAYS iced at the positions: roof-rack. the lid of the trunk, hood , ...

*December 15, 2009*

**math**

95/100 80/100 3/9 6/8 2/3

*December 15, 2009*

**Calculus**

{28/3[7/3(x^4/3) +11/5(x^2/5) +13)][x^7/3+11/7x^7/5+13x^7/7]^1/3}

*December 13, 2009*

**algebra**

= a*a- +2a -3a -6 = a(a+2)-3(a+2) = (a-3)(a+2)

*December 11, 2009*

**algebra**

4x^2 -20x +25

*December 11, 2009*

**algebra**

sorry I made mistake, the product is 6x^2 -x -2

*December 11, 2009*

**algebra**

6^x2-x-2

*December 11, 2009*

**math**

=x+y/(x+y)(x-y)/48 =48/x-y

*December 11, 2009*

**chemistry**

2molK + 1molClgas create 2molKCl nK/nClgas=2/1 5/39:7/31=1.3 so Cl gas excess mClgas(excess) = 7-(5*71/78) = 2.45g

*December 11, 2009*

**Calculus**

you can do like this: (4x^2-3)^1.5 = (4x^2-3).sq(4x^2-3)dx Let 2x = Sq3.sec(det) so, 4x^2 -3 = 3.sec^2(det)-3 = 3.tan^2(det) new INT= INt(3^1.5tan^3(det)d(det) Use Pythagore to solve the relation between x and the angle det.

*December 10, 2009*

**physics**

In a double slit experiment with a single electron, a very thin film of fluorescent material that emits a photon whenever an electron passes through is placed on one of the slits to check which slit the electrons goes through. Describe the resulting pattern on the detecting ...

*December 10, 2009*

**physics**

In a double slit experiment with a single electron, a very thin film of fluorescent material that emits a photon whenever an electron goes through. Describe the resulting pattern on the detecting screen if the experiment is repeated many times.

*December 10, 2009*

**physics**

Thank you drwls, My problem is a. The lifetime of the levels in a hydrogen atom are of the order 10-E8s. What is the evergy uncertainty of these states? Compare this result with the energy value of the first excited state. b. Find the shortest and the longgest wavelengths of ...

*December 8, 2009*

**phys.**

the shortest and longest wavelength series in singly ionized helium is 22.8nm and 30.4nm . Are they right? How many orders we can see between the angles range observations 30 and 90 in the Balmer's series?

*December 8, 2009*

**physics**

The atoms in gas ( gas constant R=8.31 J/mol K) can be treated as classical particles if their de Broglie wavelength L is much smaller than the average separation between the particles d. Consider monatomic helium gas (mHec^2 = 3727 MeV, molar mass 4g/mol) at 1.0 atmosphere of...

*December 7, 2009*

**physics**

The atoms in gas ( gas constant R=8.31 J/mol K) can be treated as classical particles if their de Broglie wavelength L is much smaller than the average separation between the particles d. Consider monatomic helium gas (mHec^2 = 3727 MeV, molar mass 4g/mol) at 1.0 atmosphere of...

*December 7, 2009*

**Physics**

The atoms in a gas (gas constant R=8.31 J/mol-K) can be treated as classical particles if their de Broglie wavelength ƒÉ is much smaller than the average separation between the particles d. Consider monatomic Helium gas (mHec2 = 3727MeV), molar mass 4g/mol) at 1.0 ...

*December 7, 2009*

**Theory and History of Visual Communication**

In shape relationships, what can you do to make objects or text seem like they are grouped together. How does repetition help create unity? Why would this be a helpful thing to do? Why would similarity in shapes create harmony? What could you do to keep harmony but make the ...

*January 24, 2007*

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