Question

Question 6: Andwer the questions about Alum Synthesis in parts A through E (see image for entire question)

6. (7 pts) Answer the questions about Alum Synthesis a) What reagent is od teirde cne H2SO4 HNO NaOH b) What gas is formed in the reaction of aluminum metal with aqueous sodium hydroxide? O2 H2 CO2 c) When HaSO4 is added to the solution containing Al(OH)s a white precipitate is formed. What is the chemical formula of this precipitate? (circle one) Al203 Al(OH)3 AIK(SO4)2 . 12H20 d) A student was recrystallizing the alum. As the hot solution cooled to roonm temperature, no crystals appeared. The flask was then placed in an ice-water bath. Suddenly a large amount of solid material appeared in the flask. The student isolated a good yield of product, however, when she tested the melting point of the product, she found it was contaminated with impurities. Explain what went wrong. Before the student filter the crystalline, what is the purpose of rinsing the crystalline with ice cold water instead of warm water? e)

Answer 1

2.Al(s) + 2NaOH + 6H20(I) → 2NaAl (OH)4(aq)-3H2(g)

2NaAl (O H) 4(aq) + H2SO4 → 2Al (OH)3(s) Ņa2SO4(aq) 2H2O(1)

$NaAl(OH)_{4}(aq) + 2H_{2}SO_{4}(aq) + 8H_{2}O(l) \rightarrow NaAl(SO_{4})_{2}.12H_{2}O(s)$

a)

NgOt

b)

Hy

c) $Al(OH)_{3}$

d) The student did not filter the hot solution to remove the insoluble impurities before allowing it to recrystallize.

e) The crystals of alum are not soluble in ice cold water and hence the water, while washing removes only the impurities.