Chemistry practicals + new spec

Why is an absolute uncertainty more impactful on y than x?

Same absolute uncertainty value but y has a smaller DV so greater proportion of result

What is the colour of a molecule if it does not absorb any colours from visible light spectrum?

White

Identify ways of preventing the oxidation of a molecule like vitamin C

• Store at lower temperature

• Store in airtight container

• Store in opaque container

Why might the colour of a solution revert back to original colour after the end point has been recored in a titration?

Equivalence point no reached

Suggest why it is important to hypothesis on the outcome of experiments

scientific claims must be falsifiable

what are the environmental advantages of operating swimming pool at a lower temperature:

• Reduced production of greenhouse gases e.g. CO2 from combustion of fossil fuels to produce energy

• Less evaporation of water

If nothing leaves or a enters the system it is known as a….

closed system

Why is chlorine not added to swimming pools (or anything) directly?

It is toxic

Ascorbic acids practical control variables

• Temperature 

• Light intensity

• Type of orange juice use

• SURFACE area of juice exposed 

What pair of techniques can be used to separate and isolate a soluble compound from an insoluble one?

1. Dissolve solution

2. Filter out insoluble particles

3. Crystallise substance to isolate

What can be used to separate two immiscible liquids??

Separatory funnel:

• Less dense solution will rise to top

• More dense solution will fall to bottom

What method can be used to separate a mixture of different boiling points?

Distillation

What is an advantage of thin layer chromatography over paper chromatography?

Separated components can be recovered as a pure substance by scraping them off of the thin layer solid UNLIKE paper chromatography

Why does the emission spectrum converge toward the violent end of the spectrum

because energy levels converge at higher levels

What are the assumptions of ideal gases and how do they contrast to real gases?

• Collisions are perfectly elastic

• Particles occupy a negligible volume (not true)

• Particles have no attractive forces between them (not true)

• The temperature of gas is proportional to the average kinetic energy

What are the arguments for and against scandium being a transition metal

For:

• Partially complete D sub shell

Against:

• Only forms ONE ions i.e. does not demonstrate variable oxidation states

• Does not form an ion with a partially complete d sub shell i.e. Sc³⁺

How is the electrochemical series arranged

increasing ability to split d orbital

What is the FUNCTIONAL GROUP name of the following classes of organic compounds:

• alkene

• alkyne

• alcohol

• carboxylic acid

• amide ( O=C-NH2)

• ether (C-O-C)

• benzene

• alkenyl

• alkynyl

• hydroxyl

• carboxyl

• amido

• alkoxy

• phenyl

Describe what is happening at the anode and the cathode of a hydrogen fuel cell

• Anode: oxidation of H₂

• H₂ → 2H⁺ + 2e^-

• Cathode: reduction of H⁺ with O₂ to form water

• 4H⁺+ 4e^- + O₂ → 2H₂O

What are the products of hydrogen fuel cell using ethanol

Anode: carbon dioxide, H+, e-

Cathode: water

What is an advantage of using the hydrogen fuel cell to release energy as opposed to fossil fuels

The only waste product is water

Distinguish between fuel and voltaic cells

Fuel cells = constant energy supply whereas voltaic cells have a set number of reactant mols