Recent content by sci-doo

Ok, let's get back to the HCl. I don't know the pH of Cl- but like you said its really weak and thus i guess quite neutral (7). Shouldn't the conjugate acid hydrogen chloride be pKa = pKw - pKb = 14-7=7 then neutral too (in aq). Don't make any sense. I've always thought that weak acid must...

Like in this http://www.chemguide.co.uk/physical/acidbaseeqia/buffers.html" where buffer solutions are explained it is said: Ammonia is a weak base, and the position of this equilibrium will be well to the left but later: The ammonium ion is weakly acidic, and so some of the hydrogen...

But still, if you make a buffer solution from weak acid or base (with corresponging strong conjugates), its the same thing as making it from strong acid or base (with weak corresponding conjugates), isn't it? So instead of making buffer solutions from weak acid and strong (conjugate) base or...

Buffer solutions are supposed to be made of weak acid and its conjugate base or weak base and its conjugate acid. BUT: weak base has a strong conjugate acid and vice versa. So I could make a buffer solution from Cl- ions (really weak base) and HCl (conjugate acid). But that's the same as...

:smile: Ok, I got a solution -3a2pi What I did I made \overline{r}(t) = a cos t + a sin t where 0 \leq t \leq 2 \pi and then dot product of F(r) and r'(t) I integrated that from 0 to 2pi with respect to t. Can I somehow expect a negative result?

Homework Statement Calculate \int \int _{S}\nabla \times \overline{F} \cdot \hat{N}dS where \overline{F} = 3y\hat{i} - 2xz\hat{j} + (x^{2}-y^{2})\hat{k} and S is a hemispherical surface x2 + y2 + z2 = a2, z ≥ 0 and \hat{N} is a normal of the surface outwards. Can you use Stokes' theorem...

Thanks!

Homework Statement What is the flux of vector field F = xi + zj out of the cube that has corners in (0,0,0),(1,0,0),(0,1,0),(0,0,1),(1,1,0),(1,0,1),(0,1,1),(1,1,1). The Attempt at a Solution Is it 1? Divergence = del dod F = 1 Triple integral of divergence= SSS 1 dx dy dz each from 0...

Homework Statement Let f(x,y,z)= |r|-n where r = x\hat{i} + y\hat{j} + z\hat{k} Show that \nabla f = -nr / |r|n+2 2. The attempt at a solution Ok, I don't care about the absolute value (yet at least). I take partial derivatives of (xi + yj + zk)^-n and get \nabla f =...

Thank you for correcting my somewhat unusual (and wrong!) approach.. I didn't see the z-part of Q as it is. Dot product is (of course): \bar{PQ}.n = fx(a,b)(x-a) + fy(a,b)(y-b) - fx(a,b)(x-a) - fy(a,b)(y-b) = 0 Once again, thank you for your help.

Q and P are given as scalars. P=(a,b,f(a,b)) is, I think, relatively easy to vectorize ai + bj + f(a,b)k Q is a bit ugly xi + yj + f(a,b)k + fx(a,b)xi - fx(a,b)ai + fy(a,b)yj - fy(a,b)bj and so Q - P is xi + yj + fx(a,b)xi - fx(a,b)ai + fy(a,b)yj - fy(a,b)bj - ai - bj and as k is gone, can...

To get PQ I think I should start with Q-P. But it is scalar and I don't see how it turns into a vector. Q-P= x,y,f(a,b) + fx(a,b)(x-a) + fy(a,b)(y-b) - a,b,f(a,b)

I get n dot PQ = fx(a,b)(x-a)+fy(a,b)(y-b)-f(x,y)+f(a,b) I still have those partial derivatives, and I don't know what to do with them.

Homework Statement Tangent plane goes through point P=(a,b,f(a,b)). Any point on the plane is then Q=(x,y,z)=(x,y,f(a,b)+fx(a,b)(x-a)+fy(a,b)(y-b)) (fx and fy are partial derivatives) and the vector \overline{PQ} is on tangent plane. Calculate dot product n.\overline{PQ} and show...

If the z is zero, aren't we only left with a circle? man.. understanding one thing requires not understanding two.. I hope I know how to turn cartesian equations to cylindrical and spherical now. I'm really trusting on these tricks: For cylindrical: x^2+y^2=r^2 For spherical...