Homework Help v1.3

[pkzild]

Originally Posted by kazman3

Co(MnO4)2

i think that is it

wuts the original charge of the manganate ion? I might kno how to do it then

damn it where is bat

[Denny Crane]

MnO4 (-1) i think

[batman555]

Permanganate? Looks like -1 to me.

[pkzild]

k then it'd have to be Co(MnO4)3 since its cobalt III

[batman555]

Okay...:S

[Orkz]

I have a classic greek and roman mythology assignment I have to do. I was just wondering if anyone knew any well translated and compiled versions of Hesiods Theogany?

[Denny Crane]

Originally Posted by canza

ummm

Calculate the mass of 500. atoms of iron(Fe). Can anyone show me the formula?
And the work?

1mole=6.02 x 10^23 (i think)
and the molecular weight (M) of iron is whatever (cant be bothered looking it up)

therefore mass=M x (500/6.02x10^23)

[batman555]

Originally Posted by kazman3

1mole=6.02 x 10^23 (i think)
and the molecular weight (M) of iron is whatever (cant be bothered looking it up)

therefore mass=M x (500/6.02x10^23)

^ Yep. This problem is just making use of conversion factors.

Maybe including units will make it easier to see:

500 * (1 mol/1.6022x10^23 mol^-1) * (molecular weight of Fe in grams/mol)

[pkzild]

seems like this guys just askin for full solutions to a homework or an assignment...

[batman555]

I have lots of homework tonight, so I can't give you lots of details, but try this:

- Convert ounces to grams (look up the conversion factor)
- Divide that by the molecular weight of air (in my classes, we used about 29 g/mol as the molecular weight of air)
- Then multiply that by Avogadro's number

[canza]

wahh!! thx!!!!! i get it now.

[Tammy]

find all solutions to equation
sin(3θ)=0 in the interval of 0 < θ < 2pi

[Merlin]

n¶/3 where n is from 0 to 6...i think. it's been a while

[batman555]

Not totally sure how to do this, but I see two possible methods:

1. sin(3*theta) = 0

===> 3*theta = 0, pi, and 2pi

Divide each term by 3 and solve for theta.



2. Use trigonometric identities. I don't know if this is mathematically legal, but I rewrote the original equation to sin(2*theta) + sin(theta) = 0.

2sin(theta)cos(theta) + sin(theta) = 0

Factoring: sin(theta)*(2cos(theta) + 1) = 0

===> sin(theta) = 0 and 2cos(theta) +1 = 0

Solve for theta. This answer gives me different values from #1.



So really, I don't know what I'm doing. :p

[Merlin]

Can't remember trig ids so i can't see prob

Good way to doub;e check this would be to draw it out. Cause it's sin 3(theta) your frequency is 3 times normal so you'd end up with a sin curve that instead of stretching from 0 to 2¶, it'll complete three times in that space.

[Denny Crane]

theta = 0, pi/3, 2pi/3, pi, 4pi/3, 5pi/3, 2pi.

edit:
i should extrapolate on that

sin(3x)=0
3x=sin^-1(0)
0<x<2x but find to 6x

(sin^-1)0= kpi where kEZ (element of the real set of integers)
so it equals 0, pi/3, 2pi/3, pi, 4pi/3, 5pi/3 and 2pi

[Tammy]

hmm thanks you guys

[The One]

Whats the chemical writing for hychloricacid?