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Type: Posts; User: joinforfun8909

1. ## Question: Expectation and variance of a random variable

by joinforfun8909
1
Views
417

### Expectation value= -30 *0.25 -20*0.05-10*0.25...

Expectation value= -30 *0.25 -20*0.05-10*0.25 +0*0.20 +10*0.25 = -8.5

Variance can be calculated as = (-30 + 8.5)^2*0.25 + (-20+8.5)^2 * 0.05 .

I'll leave that to you to calculate !
2. ## Question: Wave laws?

by joinforfun8909
4
Views
1,640

### To add "matter waves" to the list :) [De Broglie...

To add "matter waves" to the list :) [De Broglie Relation]
wavelength = Planck's constant / Momentum
3. ## Question: Titrations: magnesium carbonate and hydrochloric acid

by joinforfun8909
1
Views
2,042

### 1.25 g is not mass of MgCO3. It is the mass of...

1.25 g is not mass of MgCO3. It is the mass of MgCO3 with impurities. So the task is to find the mass of MgCO3 actually present.

That can be done by using the number of moles of HCl consumed...
4. ## Question: Balace the equation

by joinforfun8909
3
Views
432

### Phosphoric acid has 3 acidic protons and you can...

Phosphoric acid has 3 acidic protons and you can think of them being replaced one by one. Infojunkie's answer is correct !
5. ## Question: Calculating the quantity of heat required

by joinforfun8909
1
Views
890

### They look fine.

They look fine.
6. ## Question: How many moles of CaCL2 are in 250 mL of a 3.0 of CaCL2 solution?

by joinforfun8909
1
Views
797

If you see the answer I gave for your previous question, you'll understand how to solve this one.

Are these homework questions ?
There is a different place for them.
7. ## Question: What is the molarity of a solution that contains 17 g of NH3 in 0.50 L of solution

by joinforfun8909
1
Views
4,076

### Molecular weight of NH3 = 14 + 3 = 17 g/mol....

Molecular weight of NH3 = 14 + 3 = 17 g/mol.
moles = 17 g/ 17(g/mol) = 1 mol.

Molarity = moles / volume = 1/0.5 L = 2 M
8. ## Question: Dissociation of HF

by joinforfun8909
1
Views
1,176

### NaF is a strong electrolyte. So assume that its...

NaF is a strong electrolyte. So assume that its dissocation goes to completion and you'll have [F-]= 1 M.

The equlibrium equation is
HF <-> H+ + F-
I 1.0 0 1.0
C -x x ...
9. ## Question: Freezing point?

by joinforfun8909
4
Views
1,071

### Based on your numbers alone it may be hard to...

Based on your numbers alone it may be hard to figure out the freezing point correctly. Did you observe changes in the solution ? First appearance of cloudiness [that's basically parts of the solution...
10. ## Question: US Resident Alien on F-1, wife on F-2 [has ITIN].Does she need ITIN ?

by joinforfun8909
2
Views
593

11. ## Question: Draw a Lewis structure for NHF2

by joinforfun8909
2
Views
11,376

### Sounds correct. Just compare the structure with...

Sounds correct. Just compare the structure with NH3. It should work out similarly.
12. ## Question: US Resident Alien on F-1, wife on F-2 [has ITIN].Does she need ITIN ?

by joinforfun8909