Question

Just a simple chemistry question (I am posting it here as the Chemistry study group is DEAD)

Answer 1

Calculate the concentration of water and table salt, when 250 grams of table salt NaCl is in 3
litres of liquid. Table salt has a molecular mass of 58,5 g/mol. Give the answer in two decimal
precision.

Answer 2

I know the formula for moles and concentration, which is mol=mass/RMM
and conc=mol/volume

I did the calculations, but I am still not sure if I am correct, I got 1.42 as the final answer.
And I don't know what units it should be in, is it Molarity (that would be 1.42M) or mol/l, or mol/dm^3??
so, if anyone can tell me if I am right about the answer being 1.42 and also what units I should use, it would be great.

Answer 3

Oh, are you looking for molars?

Answer 4

mol per liter?

Answer 5

\[\frac{250g}{58.5g/mol}=4.27mol\]so the concentration will be\[\frac{4.27mol}{3L}=1.42M\]

Answer 6

great, so I was right :)
so I always have to use Molars right? M?

Answer 7

Depends on what they want. Typically it's that. Another kind of concentration is the 'molal' which is

moles of solute
-----------------
mass of solvent in kg

Answer 8

ok, btw, do you know what exactly is constant forward carrying force? is it just mass*acceleraltion? or something involving momentum?

Answer 9

I've never heard Newton's Second Law of Motion called 'constant forward carrying force'...

Answer 10

\[F=\frac{dp}{dt}\]where p is momentum and F is force. This is the 'proper' definition of force. If then, you take momentum, p, as\[p=mv\]then\[F=\frac{dp}{dt}=\frac{d(mv)}{dt}=m \frac{dv}{dt}=m a\]

Answer 11

oh, ok, because I have this simple question and I just wanted to be sure..

Answer 12

When there's no speeds are small compared to speed of light.

Answer 13

np

Answer 14

Motorcyclist (total mass 320 kg) stops from a velocity of 36 km/h in 25 s without breaking.
The same motorcyclist accelerates in the same conditions from full stop to velocity of 126
km/h in 6 s. Calculate the constant forward carrying force of the engine, if the forces
restricting the motion remain constant. Give the answer in 1 N precision.


so, I used the newton's second law of motion and found the answer to be 1867N.
Is that right?

my calculations were like this:

converted 126km/h to 35m/s

F=\frac{dp}{dt}

F=\frac{(35*320)}{(6)}

F=1866.66
F=1867N

am I right? or did I miss something important?

Answer 15

gtg, will be back in like 15 min

Answer 16

Hey, because I'm fried (it's 230am here) and didn't want to leave you hanging, I found this website that has the question you just asked AND solution:

http://www.algebra.com/algebra/homework/testmodule/testmodule.faq

Go nuts!

Answer 17

I have to sign out - my eyes are burning -.-

Study hard!

Answer 18

ok, thanks !!!
You are a real HERO!