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E = hc/lambda

E = (6.6 x 10^-34 J/s)(3 x 10^8 m/s) / (450 x 10^-9 m)

Thank you =)

The kid on the corner is running a game in which a fair coin is tossed twice. If exactly two tails occur, the player wins $5. If exactly one head occurs, the player wins $1. Otherwise the player gets nothing.

Calculate the expected value E(X).

I am having a hard time starting this question to begin to find the expected value. Can someone help me out with this? I would greatly appreciate it..

I'm supposed to do a 1500 word paper on a topic that is biology related and I do not know what I should do it on. So I decided to come on here and ask to hear some ideas =).

So what do you think I should do my paper on? It has to be biology related and something I can find books about. =)

Thanks!

The question is:

The work function of an element is the energy required to remove an electron from the surface of the solid element. The work function for lithium is 279.7 kJ/mol (that is, it takes 279.7 kJ of energy to remove one mole of electrons from one mole of Li atoms on the surface of Li metal). What is the maximum wavelength of light that can remove an electron from an atom on the surface of lithium metal?

The answer in nm.

My Calculations:

Work--> 279.7kJ/mol x 1mol/6.022x10e23 = 4.644 x 10e-22kJ

Into J --> 4.644e10-25J

Plank's Equation:

wavelength=hc/delta E

(6.626e-34J/s)(2.9979e8m/s)/(4.644e-25J)

=4.277e-01

In nm --> 4.277e-01 x 1nm/1x10^-9 = 4.277e8nm

But that answer is wrong so I am wondering what am I doing wrong??

Thank you!

How would I convert 3.97 x 10^-19 J/Photon into wavelength in meters?

I'm not sure where to start, do I need to use Delta E=hc/wavelength?

Could you maybe explain this to me in steps?

Thank you!

A system undergoes a process consisting of the following two steps.

Step 1: The system absorbs 83 J of heat while 45 J of work is done on it.

Step 2: The system absorbs 45 J of heat while performing 83 J of work.

Also, what is the rule to know which sign (+-) I use for which (work/heat)?

a) What is the pressure in torr due to CO2(g)?

b) How many moles of CO2 gas are collected? (The vapour pressure of water at 25.0*C is 23.8torr.)

How do I go about solving this question?

Where do I start and can you break down how I should do this for future questions such as these.

Thank you.

The density of liquid nitrogen is 0.808g/mL at -196 degrees celsius.

What volume of nitrogen gas at STP must be liquefied to make 10.0L of liquid nitogen?

How do I do this?

MM=dRT/P so where does volume come in when needing to find volume in this equation..

Thanks!

So if we have a redox reaction in an acidic solution:

H3AsO4 + Zn --> AsH3 + Zn2+

I know that As was reduced and gained electrons and Zn was oxidizing losing electrons which :

H3AsO4 ----> AsH3

+5 ---------> 3- (+2e-)

Zn-->Zn2+

0-->2+(+2e-)

So now my teacher who did an example on the board she began to multiply these by numbers... why did she do this?? Her example was:

NO3- + 4H+ + Zn --> NO + Zn + 2H2O

2[NO3- + 4H+ ---> NO + 2H2O]

+5 (+3e-) --------> +2

3[Zn---> Zn2+]

0 ---> 2+ (+2e-)

I'd like to know why she did this?

And would the process change for a basic solution??

HXeO4- + Pb ---> Xe + HPbO2-

Thank you!

The acid contains one acidic hydrogen per molecule. If 1.863g of the acid require 70.11mL of the NaOH solution, what is the molar mass of the acid?

I feel like I know how to do this question but I am not sure. Do I use the molarity equation and start off like this...

0.1392M=moles/0.07011L..

Can you walk me through this question?

Thank you!

How many mL of 0.50M Ca(OH)2 are required to react with HCl in 30mL of a 0.12M solution?

So when I completed the calculations using M1V1=M2V2 I got 7.2mL but the answer is half of that which is 3.6mL.

I would like to know why is it half..?

If you have any two gases in different containers that are the same size at the same pressure and same temperature, what is true about the moles of each gas?

There will be more moles of the gas with the lower atomic mass.

There will be more moles of the gas with the greater atomic mass.

The moles of each gas are equal.

.

Why is this true?

Whenever I print pictures, faded lines appear throughout the photo, how do I fix this? I have a Canon i560