## anonymous 5 years ago Just a simple chemistry question (I am posting it here as the Chemistry study group is DEAD)

1. anonymous

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.

2. anonymous

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.

3. anonymous

Oh, are you looking for molars?

4. anonymous

mol per liter?

5. anonymous

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

6. anonymous

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

7. anonymous

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

8. anonymous

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

9. anonymous

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

10. anonymous

$F=\frac{dp}{dt}$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$F=\frac{dp}{dt}=\frac{d(mv)}{dt}=m \frac{dv}{dt}=m a$

11. anonymous

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

12. anonymous

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

13. anonymous

np

14. anonymous

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?

15. anonymous

gtg, will be back in like 15 min

16. anonymous

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!

17. anonymous

I have to sign out - my eyes are burning -.- Study hard!

18. anonymous

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