# Amount of Substance Flashcards Preview

## A-level AQA Chemistry - Physical > Amount of Substance > Flashcards

Flashcards in Amount of Substance Deck (17)
1
Q

A

Number of particles= Number of Moles x Avagadro’s Constant

2
Q

Formula for moles, mass, mr

A

Number of Moles= Mass of Substance -:- Mr

n=m -:- mr

3
Q

Formula for calculating moles in solution

A

Number of Moles= Concentration (mol dm-3) x Volume (dm3)

n=cv

4
Q

Ideal Gas Equation

Describe each part and give the units

A

pV=nRT

```p= pressure (Pa)
V= volume (m3)
n= number of moles
R= 8.31 J K-1 mol-1
T= temperature (K)```
5
Q

Changing temperature from oC to K

A

K= oC +273

6
Q

1cm3 in m3

1 dm3 in m3

A

1 cm3 = 1 x 10-6 m3

1 dm3 = 1 x 10-3 m3

7
Q

Standard Solution (aka volumetric solution)

Making a Standard Solution

A

Any solution that you know the exact concentration of.

Involves dissolving a known amount of solid in a known amount of water to create a known concentration

8
Q

Empirical Formula

A

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

9
Q

Molecular Formula

A

The actual numbers of atoms of each element in a compound.

A whole number of empirical units

10
Q

Percentage Yield

A

Actual Yield -:- Theoretical Yield x 100

11
Q

Percentage Atom Economy

A

Molecular Mass of Desired Product -:- Sum of molecular masses of all reactants x 100

12
Q

Spectator Ion

A

An ion that’s present in the reaction mixture, but doesn’t get involved in the reaction

13
Q

Describe how to set up a titration (in full)

A

Use a pipette to measure out a set volume of the solution that you want to know the concentration of. Put it in a flask.

Fill a burette with a standard solution of the acid.

Use a funnel to carefully pour the acid into the burette. Always do this below eye level to avoid any acid splashing onto your face or eyes (wear safety glasses)

14
Q

Describe how to conduct an accurate titration

A

Firstly, do a rough titration to get an idea of where the end point is.
Add acid to the alkali using a burette, giving the flask a regular swirl.

Place the flask over a white tile to clearly see when the colour change occurs (ie when the end points is).

Do an accurate titration. Take an initial reading to see exactly how much acid is in the burette. Then run the acid in to within 2 cm3 of the end point.

When you get to this stage, add it dropwise. If you don’t notice exactly when the colour changes you’ll overshoot and your result won’t be accurate.

Work out the amount of acid used to neutralise the alkali. This is just the final reading minus the initial reading. This volume is known as the titre.

Repeat the titration a few times, until you have at least three results that are concordant (within 0.1 cm3 of each other).

Use the concordant results to calculate the mean (average) volume of acid used

15
Q

End Point

A

The exact point where the alkali is neutralised and the indicator changes colour

16
Q

Methyl Orange

A

Red in acid

Yellow in alkali

17
Q

Phenolphthalein

A

Colourless in acid

Pink in alkali