8B.6

Question 1

what is a flame test

Answer 1

a very simple chemical test used to identify a cation (charged) in chemical compounds

Question 2

how do you run a flame test

Answer 2

1. wear a lab coat and safety goggles, within a fume cupboard light a bunsen flame
2. using a dropper add a few drops of HCl into the metal compound and mix them together for them to begin to dissolve.
3. take a clean metal wire (platinum and nichrome) or a silica rod and dip it into the mixture to obtain a sample of the compound
4. hold the end of the wire above the flame and observe the colour

Question 3

what is the reason for using HCl in the compound

Answer 3

because metal chlorides are more volatile than any other salt so we would have better results

Question 4

what is the problem with flame tests

Answer 4

1. many compounds contain small sodium compound as an impurity, the intense light of sodium can hide other colours
2. describing colours with words is subjective

Question 5

what colour does Li form

Answer 5

red

Question 6

what colour does Na form

Answer 6

yellow/orange

Question 7

what colour does K form

Answer 7

lilac

Question 8

what colour does Rb form

Answer 8

red/purple

Question 9

what colour does Cs form

Answer 9

blue/violit

Question 10

what colour does Mg form

Answer 10

no colour

Question 11

what colour does Be form

Answer 11

no colour

Question 12

what colour does Ca form

Answer 12

brick red

Question 13

what colour does Sr (strontium) form

Answer 13

crimson red

Question 14

what colour does Ba form

Answer 14

apple green

Question 15

what colour does Cu form

Answer 15

blue-green (even thou transitional metal)

Question 16

what does groud state mean?

Answer 16

it is a term used to describe an atom with all its electrons in their lowest possible energy level

Question 17

what is an exited state

Answer 17

when an electron in a ground state is heated and goes up to a higher energy level

Question 18

how are colours shown during flame tests

Answer 18

when a cation is heated the electrons would absorb energy and go to a higher energy level and become in an excited state, but the electron then returns to its original state. and energy is released, if the energy corresponds to specific radiation in the visible light spectrum the characteristics of that light is shown

Question 19

why does Mg have no colour

Answer 19

because the electron transition in Mg corresponds to a wavelength outside the visible light spectrum

Question 20

what are the tests for ammonium ions s

Answer 20

1. add sodium hydroxide solution plus warmth to an ammonium mixture the earth causes ammonia gas to be released, ammonia can be detected by smell but using a damp litmus paper turns blue is an easy chemical test
2. we can add hydrogen chloride gas (from concentrated HCl acid) to ammonia mixture and white smoke of ammonium chloride forms

Question 21

what is the net ionic equation for ammonium and sodium hydroxide

Answer 21

NH4^+ + OH^- ——–> NH3 + H2O

Question 22

what is the equation between ammonia and hydrogen chloride gas

Answer 22

NH3 + HCl ——> NH4Cl