Forgotten Units: kg, m/s^2, cm^3, mL Explained

[nemzy]

What does (kg)(m/s^2) = what unit?

also does 1 cm^3= 1 mL?

i forgot all these units stuff its really bugging up my mind

 

[Pyrrhus]

(kg)(m/s^2) = Newton

1 cm^3= 1 mL Yes

 

[nemzy]

ok, I am confused, I've been stuck on this problem for about an hour

So far i got this in my calculations:

(5.316 L*atm) / ( (211.68 kg*m/s^2)+(.0073m^2*atm))

the answer is suppose to be in meters, and from these units i have no idea how it is possible..anyone have any ideas?

 

[Pyrrhus]

Show your work, by the way, L is liters right?

 

[nemzy]

oh yeah and 1 more question, if u add units, then what happens?

like for example, if u have 8 atm + 3 liters, will it become 11 (atm+liters)?

 

[nemzy]

k here is my work:

the equation is this:

h=n*R*T/(m*g+Po*A)

n= 1.85 moles
R=gas constant
T= 350 K
A= .00730 m^2
m= 21.6 kg

and Po is atmospheric pressure (1 atm or 1.0135e5 kPa)

 

[Spectre5]

Absolutely Not!

 

[Pyrrhus]

I don't believe you can do that, look up atm basic units, i mean Newton is kg*m/s^2, what is atm equal to? and use the relation above cm^3 = mL, and see if you can follow from that. This problems can be solved by converting to the same types of units, and simple elimination of analogous units.

 

[Spectre5]

that last post was directed at the previous post...about adding units

 

[Pyrrhus]

a Pascal is N/m^2, use that. Also 1 atm = 101325 pascal.

 

[nemzy]

ok, so i ended up with this:

5.315975 L*atm / (211.68 N +739.6725 m^2*Pa)

but i am stuck here, how can i cancel out further units? since the bottom is addition, i have no idea what to do from here...am i still allowed to convert the m^2 to liters and cance it out with the top, as well as the Pa with the atm on top?

 

[Spectre5]

well, a pascal times m^2 is just Newtons!

so you have all Newtons on the bottom...then instead of using that gas constant...use the one that is J * mol^-1 * K^-1

then you have J / N...which is meters (change them to their base forms if you want to double check it :) )

 

[Pyrrhus]

nicely done

 

[Spectre5]

gas constant:

8.314 J * mol^-1 * K^-1

instead of

8.2057 L * atm * mol^-1 * K^-1

there are a few other forms of the gas constant too, but these are the most commonly used ones.

 

[nemzy]

thx! i finally got the right answer..this units are really bugging

does anyone know a website that has all these info?

 

[Pyrrhus]

It should be on your textbook, if not try google.