2. Group - 3
Md. Jahirul Islam 2014000300050
Md. Mahmudul Hasan 2014000300051
Ishtiaq Ahmed 2014000300052
Md. Tanvir Islam 2014000300053
Anisur Rahman 2014000300054
Jahirul Islam Jahir 2014000300055
Saeema Sultana 2014000300056
3. Sodium Salt
Introduction: Sodium dichromate is the chemical
compound with the formula Na2Cr2O7. However, the
salt is handled as its dihydrate Na2Cr2O7·2H2O.
Virtually all chromium ore is processed via conversion
to sodium dichromate.
Reaction:
2 Cr2O3 + 4 Na2CO3 + 3 O2 → 4 Na2CrO4 + 4 CO2
4. Preparation:
Sodium dichromate is generated on a large scale from ores
containing chromium(III) oxides. The ore is fused with a
base, typically sodium carbonate, at around 1000 °C in the
presence of air (source of oxygen).
Step 1:
Solubilizes the chromium and allows it to be extracted into
hot water. At this stage, other components of the ore such
as aluminium and iron compounds, are poorly soluble.
5. Step 2:
Acidification of the resulting aqueous extract with sulfuric
acid or carbon dioxideaffords the dichromate, which is
isolated at the dihydrate by crystallization.
Step 3:
A variety of hydrates of this salt are known, ranging from
the decahydrate below 19.5 °C as well as hexa-, tetra-, and
dihydrates. Above 62 °C, these salts lose water
spontaneously to give the anhydrous material.
6. Final Step:
Secondary alcohols are oxidized to the corresponding
ketone, e.g. menthol to menthone ; dihydrocholesterol to
cholestanone:
3 R2CHOH + Cr2O7
2- + 2 H+ → 3 R2C=O + Cr2O3 + 4 H2O
7. Potassium Salt
Introduction:
Potassium chloride occurs naturally as sylvite, carnallite,
and potash, and it can be extracted from these ores.
Reaction:
KOH + HCl → KCl + H2O
2 K + Cl2 → 2 KCl
8. Preparation:
Potassium chloride is inexpensively available and is rarely
prepared intentionally in the laboratory.
1) It can be generated by two routes that are of instructive
but not practical value: One way is to treat potassium
hydroxide (KOH) with hydrochloric acid.
KOH + HCl → KCl + H2O
9. 2) This conversion is an acid-base neutralization reaction.
The resulting salt can then be purified by recrystallization.
3) Another method would be to allow potassium to burn in
the presence of chlorine gas, also a very exothermic
reaction:
2 K + Cl2 → 2 KCl
10. Uses:
Medical use of Sodium chloride:
Tablets: Sometimes, there is excessive loss of sodium
from our body due to dehydration or excess sweating.
Intravenous saline (IV): One of the properties of salts
is that it rises blood pressure
Ophthalmic ointment: In some cases, solution of
sodium chloride is used to treat swelling of cornea in the
eye.
11. Potassium Salt:
This medication is a mineral supplement used to
treat or prevent low amounts of potassium in the
blood.
Potassium chloride should be used with caution in
the elderly, those with kidney problems, heart
problems, conditions causing a narrowing or blockage
of the gut (intestine), stomach ulcer, hiatus hernia,
metabolic acidosis nad those with Addisons disease.