Moles 2 - Gases

Question 1

The ideal gas equation

Answer 1

pV = nRT
p= pressure (Pa)
V= volume (m^3)
T= temperature (K) (°C+273)
n= amount of substance (moles)
R= gas constant (8.31)

Question 2

converting to m^3

Answer 2

cm^3 —> m^3 = /10^6
dm^3 —> m^3 = /10^3

Question 3

When do we use the ideal gas equation?

Answer 3

When we do not have room temperature or pressure

Question 4

What assumptions are made when dealing with the ideal gas equation

Answer 4

-assume gas molecules are tiny compared to the space between them
-no forces are acting between the gas molecules
-gas molecules move randomly
-when the gas molecules collide, the collisions are elastic

Question 5

What is atom economy

Answer 5

atom economy tells us what percentage of the mass of the reactant atoms end up in the product we want

Question 6

Calcuating atom economy

Answer 6

Atom economy (%) = (molecular mass of desired product / sum of all molecular masses of all reactants) * 100
(assuming percentage yied is 100%)

Question 7

What is percentage yield

Answer 7

Comparison of the product actually obtained with what could have beeb obtained theoretically, if all reactants were converted with no loss or waste

Question 8

Reasons as to why it is rare to achieve mas. theoretical yield

Answer 8

-not all reactant may react (esp. in reversable reactions)
-side reactions - making other products
-product lost e.g. during filtration

Question 9

Calculating percentage yield

Answer 9

Yield (%) = (actual yield / theoretical yield) * 100

*either use grams for both or moles for both

Question 10

Limiting reagent

Answer 10

The chemical used up first

Amount in moles of limiting reagent = amount of product that can be made