3.3 moles and volumes

Question 1

unit conversions

cm^3 -> dm^3

Answer 1

divide 1000

Question 2

dm3 -> cm3

Answer 2

X 1000

Question 3

Cm3 to ml

Answer 3

1cm3=1ml

Question 4

Idm3 to Liters

Answer 4

1dm3=1L

Question 5

Calculate

Number of moles

with concentration and volume

Answer 5

Conc (mol/dm3) X vol (dm3)

Question 6

What is the

ideal gas equation

Answer 6

PV=nRT

Question 7

what are the units for

PV=nRT

Answer 7

P- pressure (pa)
V-volume (m3)
n- number of moles (mol)
R- gas constant (J/mol/k)
T- temprature (K)

Question 8

Unit conversion

kPa -> Pa

Answer 8

X1000

Question 9

Unit conversion

K->.c

Answer 9

-273

Question 10

When do we use the

ideal gas equation

Answer 10

differnet temps and pressures for greater accuracy we use the ideal gas equation

Question 11

What are the assumptions made about

the ideal gas equation

Answer 11

1. the molecules are in random motion
2. elastic collisions
3. negligible size
4. no intermolecular forces

Question 12

In PV=nRT

whats the value of the constant R

Answer 12

8.314

Question 13

Define

A standard solution

Answer 13

is a solution whose concentration is known.

Question 14

which glassware is used to make a standard solution.

Answer 14

volumetric flask

Question 15

The tolerances of the volumetric flask

Answer 15

100cm3 volumetric flask: +/- 0.20cm3

250cm3 volumetric flask: +/- 0.30cm3

Question 16

Where should the meniscus sit?

Answer 16

When filling a volumetric flask, the meniscus of the
solution must sit on the graduated line

Question 17

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?

Answer 17

There would be uneven mixing of the substance within the standard solution. Inverting the
flask allows uniform mixing, and an equal concentration throughout.

Question 18

What effect will overfilling the volumetric flask beyond the graduated mark have?

Answer 18

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.

Question 19

Making a standard solution:

Answer 19

1. Weigh the exact mass of solid accurately.
2. Dissolve the solid in a beaker using less distilled water than will be needed to fill the volumetric flask to the mark.
3. Transfer the solution to the volumetric flask. The last traces of the solution are rinsed into the flask with distilled water.
4. 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.
5. 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.)

Question 20

!!! If n = cxV/1000 is used to calculate the concentration, multiplying your answer by the Mr
of the compound will give the concentration in gdm-3

Answer 20

If n = cxV/1000 is used to calculate the concentration, multiplying your answer by the Mr
of the compound will give the concentration in gdm-3

Question 21

g/dm3->mol/dm3

Answer 21

divide by Mr