# Chapter 3: Amount of substance (3.1-3.4) Flashcards

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1
Q

Water of crystallisation

A

water molecules that form an essential part of the crystalline structure of a compound.

2
Q

Moles =

A

mass / Mr

3
Q

How do you work out the water of crystallisation?

A

1) Calculate the amount, in mol, of the anhydrous salt formed
2) Calculate the mass and amount , in mol, of water
3) Divide by the smallest number of moles: simplest whole number ratio
4) Write down the value of X and write in the formula of the salt

4
Q

A

6.02x10^23

5
Q

Anhydrous

A

a substance containing no water molecules

5
Q

Hydrated

A

Crystalline and containing water molecules

6
Q

Why may the mass of anhydrous salt not be what you expected after heating?

A

1) Some of the water may not have been removed

2) Heating could have caused the salt to decompose

7
Q

Ideal gas equation

A
```pV = nRT
p = pressure in Pa
V = volume in M[3]
n = number of moles
R = the gas constant 8.31Jk[-1]mol[-1]
T = temperature in K```
8
Q

Likely conversions to be made when using ideal gas equation

A

Cm3 -> m3 = 10^-6
Dm3 -> m3 = 10^-3
°C -> K = +273
kPa -> Pa = 10^-3

9
Q

Why are reactions with high atom economies good?

A

1) Produce a large proportion of desired products and few unwanted waste products
2) Important for sustainability as they make the best use out of natural resources

10
Q

Atom economy equation

A

atom economy (%) = (sum of molar masses in desired product / molar masses of all products) X 100

11
Q

% yield equation

A

(useful output/total input) X 100

12
Q

Gas calculations at RTP

A

volume (dm[-3]) = moles (n) X 24

13
Q

Working out Mr from density

A

Mr = density x 24000