Prepare this Data Table in your lab notebook before arriving at the lab: Write a
ID: 489408 • Letter: P
Question
Prepare this Data Table in your lab notebook before arriving at the lab: Write a balanced equation for the decomposition by heating of iron(II) sulfate hepatahydrate. Calculate the molar mass of iron(II) sulfate heptahydrate in 4 sig. fig. Calculate the theoretical % of H_2O in iron(II) sulfate heptahydrate in 4 sig. fig. In the reaction described in Question #1, a) What is the formula of the hydrate? b) What is the formula of the anhydride? c) How many molecules of water of hydration arc in each formula unit of the hydrate? 5. A sample of hydrate is being heated in a crucible to determine its water content as described in the experiment. What is the criterion for deciding whether a third heating is necessary? Be specific and explain your answer. What is the proper way of using crucible tongs, and why is it best done that way?Explanation / Answer
Pre-Lab exercise:
1. Decompostion reaction by heating of Iron(II)sulfate heptahydrate is shown in a chemical reaction as follows:
FeSO4.7H2O ---------> FeSO4 + 7H2O
2. Molar mass of Iron(II)sulfate heptahydrate = Atomic mass of Fe + Atomic mass of S + (14 x Atomic mass of H) + (11 x Atomic mass of O)
= 55.85 + 32 + (14 x 1) + (11x 16)
= 277.85 g/mol
= 277.8 g/mol (rounded to 4 sig.fig)
3. Molar mass of Iron(II)sulfate heptahydrate = 277.8 g/mol
Mass of water present in it (7H2O) = 7 x 18 = 126 g
Thus, 277.8 g of Iron(II)heptahydrate consists of 126 g of water
Percent of water = (126 / 277.8) x 100 = 45.36 %
4. a) The formula of the hydrate is FeSO4 .7H2O
b) The formula of anhydride is FeSO4
c)Each formula unit of hydrate has 7 water molecules.
5. During heating process in the experiment, we take mass of crucible + hydrate in 1st heating and in 2nd heating. If there is no decrease in weight after 2nd heating (no loss of water), it is clear that there won't be any decrease in weight after 3rd heating (loss of water). So, we can stop at 2nd heating step.
6. Crucible tongs are scissors like equipment which are used to hold crucible and move it from furnace to other places. It is should be used after wearing proper gloves. It is used as such because, the furnace has high temperatures.