Q3 When dry
cobalt(II) chloride paper is dipped into a liquid, it turns blue. What can you
deduced?
✘ans: The liquid is water
What’s WRONG?
Dy cobalt(II) chloride
paper turns blue only if the liquid contain water. That mean NaCl solution,
NaOH solution also can turn the paper blue. So we only can deduce the solution
contain water.
✘ans: We can carry out flame
test which give greenish flame
What’s WRONG?
Flame is used to test
metal ion but not metal. To test copper, HNO3 can be used which
blown gas is given out and blue solution is observed.
Cu + NO32-
+ H+ → Cu2+ + NO2
+ H2O
H2SO4
is also used which give colourless bubble and blue solution.
Cu + SO42- + H+ → Cu2+ + SO2 + H2O
Q1 What is the relative atomic mass of Mg?
✘ans: relative atomic mass of
Mg = 24.3 g
What’s WRONG?
Relative
atomic mass should have no unit because it is relative
relative atomic mass of Mg = 24.3 g
molar mass of Mg = 24.3 g mol-1
沒有留言:
張貼留言