Elements Of Life

Question 1

Give the relative mass and charge of the following subatomic particles.

p+

n0

e-

Answer 1

p+ = 1, +1

n0= 1, 0

e-= 1/2000, -1 mass is negligible

Question 2

What are isotopes?

Comment on their chemical properties/rxns

Answer 2

• Atoms of the same elements with the same number of protons and electrons but different number of neutrons.
• same number of e- so react similarly
• small physical difference: higher mass = higher mlt/boiling points.e.g heavy water

Question 3

What did the following individuals think about the structure of an atom?

• J.J Thompson
• Rutherford
• Bohr + Chadwick

Answer 3

• Plum Pudding-Electrons embedded in a positive sphere
• Gold foil experiment- atom mostly empty space with most mass in nucleus with orbiting e-
• Bohr- orbits around nucleus
• Chadwick- neutrons

Question 4

What is the relative atomic mass?Ar

What is the relative isotopic mass?

Answer 4

• weighted mean mass of an atom of an element relative to 1/12th of the mass of a carbon-12 atom.
• mass of an atom of an isotope of an element relative to 1/12th of the mass of a carbon-12 atom.

Question 5

What are the steps involved in mass spectrometry?

Answer 5

• V- vaporisation into a gas
• I- ionisation bombarded with high energy electrons leaving positive ions
• A- acceleration by an electric field
• D- detection time taken for + to reach drtrctor. depends on ions mass + ccharge.

Question 6

Describe the trends in frequency/energy and wavelength across the electromagnetic spectrum.

Answer 6

-Frequency/energy is lowest at Radio waves and highest at Gamma rays. -Wavelength is the lowest at gamma rays and highest at radiowaves.

Question 7

Atoms in their ground state have……..

Answer 7

all their electrons in the lowest possible energy levels

Question 8

If electrons can take in energy from their surroundings……

Answer 8

they can be excited to a higher energy level

Question 9

Electrons can release energy……

Answer 9

by dropping from a higher energy level down to a lower energy level.

Question 10

What do absorption spectra look like?

What about emission spectra?

Answer 10

Absorption: Black lines on a coloured background.

Emission: Coloured lines on a black background.

Question 11

How are Absorption spectra made?

Answer 11

• Energy is related to frequency.
• When EM radiation passes through a gaseous element
• electrons only absorb certain frequencies = differences between energy levels
• Radiation passing through has frequencies missing.
• The dark lines are the missing frequencies.

Question 12

How are Emission spectra made?

Answer 12

• Electrons give out certain amounts of energy when they drop
• each element has a different electron arrangement
• so frequencies of radiation absorbed and emitted are different.

Question 13

Draw a labelled diagram to explain why spectra are unique for individual elements.

Answer 13

• Electrons are excited to higher energy levels by adding energy.
• Energy can be lost, electron drops to lower energy level releasing energy.
• Energy of drop can be calculated with ΠE=hv
• Unique spectra due to different gaps between E levels

Question 14

Empirical formula is……….

Molecular formula is………

Water of crystallisation is……….

Percentage yield equation:

Why yield is never 100%?

Answer 14

• the smallest whole-number ratio of atoms of elements in a compound.
• the actual number of atoms of elements in a compound.
• water incorporated in the crystalline structure of some compounds
• (actual yield/theoretical yield)X100
• reactans not reacted fully, os e.g left on filter paper

Question 15

Making a standard solution:

Answer 15

1. Work out how many moles of solute needed, how many grams
2. weigh beaker first, then add solute
3. Add small amount of distilled water and stir, put in a volumetric flask
4. Add more distilled water until 250cm3 mark, bottom of meniscus reaches line.

Question 16

Carrying out an accurate titration: