Chem

Question 1

What is a mole?

Answer 1

Amount of atoms in a substance
6.02 * 10^23 (avogadros constant)

Question 2

What are the formulas for calculating moles?

Answer 2

n = N (numer of particles)/ NA (avogadros constant)
n = M (mass, g) / Mr (molar mass, g)
n = c (mol^-1/L) * v (volume, L)

Question 3

What is a standard solution?

Answer 3

Solution of an accurately known concentration
prepared by a known mass of primary standard

Question 4

What makes something a suitable primary standard?

Answer 4

• Pure form (unmixed, not hydrated salt)
• Known chemical formula
• Able for it to be stored without deterioration and does not react with atmosphere
• high molar mass to eliminate errors when weighing
• inexpensive so it can be used a lot for accurate results.

Question 5

What are the steps to finding an unknown concentration with a known concentration in titration?

Answer 5

1. Write the balanced equation
2. Find the moles of the known using n=cv
3. Use stoichiometry ratios to find the unknown moles
4. Find the concentration of the unknown using c=n/v

Question 6

What is an aliquot?

Answer 6

small measured amount of a homogenous solution that has an unknown concentration.
Goes into the conical flask

Question 7

What is a titre?

Answer 7

Total volume of a solution delivered by a burette

Question 8

What are concordant titires?

Answer 8

Titres that have a volume 0.10mL of each other, ensures accuracy

Question 9

End point vs Equivalence point

Answer 9

endpoint:
The pH when indicator changes colour
equivalence point:
When the acid and base have neutralised with the same exact ratios (cannot be identified in titration)

Question 10

What is frequency?

Answer 10

The number of waves that pass a point per second measured in Hz (per second)

Question 11

What is a wavelength?

Answer 11

The distance from peak to peak, measured in m

Question 12

Properties of high frequency waves?

Answer 12

High frequency waves have short wavelengths
High frequency waves have high energy

Question 13

The visible region?

Answer 13

• White light consists of all colours of light in the visible region of the electromagnetic spectrum
• objects appear a certain colour due to them reflecting that wavelength and absorbing all the others.

Question 14

What is spectroscopy?

Answer 14

The idea that different solutions absorb different wavelengths of light, and that higher concentrations absorb more light than lower concentrations

Question 15

What is absorbance?

Answer 15

Initial radiation intensity - Final radiation intensity
How much light is absorbed

Question 16

What is transmittance?

Answer 16

How much light can pass through a substance,
what is emitted at the end.