3 - Amount Of Substance

Question 1

Define mole

Answer 1

Unit for amount of substance.

Number of particles in 1 mole of a substance = Avogadro’s constant = 6.02 x 10 ^23 mol^-1

Question 2

Calculate: how many moles of carbon in 1.50 x 10^24 carbon atoms?

Answer 2

Number of moles = number of particles you have / number of particles in a mole

Therefore, number of moles = 1.50 x 10^24 / 6.02x10^23 = 2.49 moles

Question 3

Define molar mass

Answer 3

Mass of 1 mole of a substance.
Same as relative molecular mass, Mr
Units : g mol^-1

Question 4

Moles equations

Answer 4

1) number of moles = number of molecules or particles you have / number of particles in a mole
2) number of moles (n) = mass (m) / Mr (M)
3) number of moles = volume in dm^3 (V) / molar gas volume , 24 dm^3 mol^-1
4) pV = nRT
5) number of moles (n) = concentration (C) x volume (v), in dm3

Question 5

Define molar gas volume

Answer 5

The space that 1 mole of a gas occupies at a certain temperature & pressure.
Units : dm^3 mol^-1

@ RTP, 24 dm^3 mol^-1 for any gas.

Question 6

Ideal gas equation, units, values, common conversions

Answer 6

pV = nRT

p = pressure, Pa
V = volume, m^3 
n = number of moles 
R = gas constant, 8.314 J K^-1 mol^-1
T = temperature, K 

cm3 to m3 = x10^-6
dm3 to m3 = x 10^-3
degrees C to K = +273
kPa to Pa = x10^3

Question 7

When do you use the ideal gas equation?

Answer 7

To find number of moles at ANY temperature and pressure

Question 8

Define empirical formula

Answer 8

the simplest whole number ratio of atoms of each element present in a compound

Question 9

Define molecular formula

Answer 9

The number and type of atoms of each element in a molecule