3.3 moles and volumes Flashcards
unit conversions
cm^3 -> dm^3
divide 1000
dm3 -> cm3
X 1000
Cm3 to ml
1cm3=1ml
Idm3 to Liters
1dm3=1L
Calculate
Number of moles
with concentration and volume
Conc (mol/dm3) X vol (dm3)
What is the
ideal gas equation
PV=nRT
what are the units for
PV=nRT
P- pressure (pa)
V-volume (m3)
n- number of moles (mol)
R- ideal gas constant (J/mol/k) 8.13
T- temprature (K)
Unit conversion
kPa -> Pa
X1000
Unit conversion
K->.c
-273
When do we use the
ideal gas equation
differnet temps and pressures for greater accuracy we use the ideal gas equation
What are the assumptions made about
the ideal gas equation
- the molecules are in random motion
- elastic collisions
- negligible size
- no intermolecular forces
In PV=nRT
whats the value of the constant R
8.314
Define
A standard solution
is a solution whose concentration is known.
which glassware is used to make a standard solution.
volumetric flask
The tolerances of the volumetric flask
100cm3 volumetric flask: +/- 0.20cm3
250cm3 volumetric flask: +/- 0.30cm3
Where should the meniscus sit?
When filling a volumetric flask, the meniscus of the
solution must sit on the graduated line
Once made up to the graduation line, the stopper is placed on top and the volumetric flask is
slowly inverted to ensure even mixing. Why?
There would be uneven mixing of the substance within the standard solution. Inverting the
flask allows uniform mixing, and an equal concentration throughout.
What effect will overfilling the volumetric flask beyond the graduated mark have?
Overfilling the volumetric flask, would increase the volume of water in which the substance
has been dissolved. This would decrease the concentration of our solution.
Making a standard solution:
- Weigh the exact mass of solid accurately.
- Dissolve the solid in a beaker using less distilled water than will be needed to fill the volumetric flask to the mark.
- Transfer the solution to the volumetric flask. The last traces of the solution are rinsed into the flask with distilled water.
- Fill the flask carefully to the graduation line by adding distilled water a drop at a time until the bottom of the meniscus lines up exactly with the mark.
- Invert the volumetric flask, slowly, several times to mix the solution thoroughly. (N.B. if this stage is not done, then you will end up with inconsistent results in your titration.)
when n=cv is used to calculate concentration simply …. by ……. to convert it to gdm-3
when n=cv is used to calculate concentration simply multiply by mr to convert it gdm-3
g/dm3->mol/dm3
divide by Mr
