IIT JEE , AIEEE Forum - Chemistry , Inorganic Chemistry

rakesh61

major part of chalk is ---- gypsum , CaCO3 , Ca , CaO

Ans is given gypsum please tell me if it is correct i think it should be CaCO3 please tell me correct ans with reason

dev_22oct

its CaCO₃

chimanshu_007

i have read somewhere its gypsum only......i too had a doubt....bt i have read it 2-3 times.....in diff books :)

dev_22oct

The main component of chalk is calcium carbonate (CaCO₃), a form of limestone. Limestone deposits develop as coccoliths(minute calcareous plates created by the decomposition of plankton skeletons) accumulate, forming sedimentary layers. Plankton, a tiny marine organism, concentrates the calcium found naturally in seawater from .04 percent to 40 percent, which is then precipitated when the plankton dies.

The base of pastel chalks is calcium sulfate (CaSO₄), which is derived from gypsum (CaSO₄-2H₂O), an evaporite mineral formed by the deposition of ocean brine; it also occurs disseminated in limestone. Chalk and dehydrated gypsum thus have similar origins and properties. Pastels also contain clays and oils for binding, and strong pigments. This mixture produces sticks that write smoothly without smearing and draw better on paper than on chalkboards. Although great care is taken to eliminate contaminants when chalk is manufactured, some impurities inherent to the mineral remain. Chief among these are silica, alumina, iron, phosphorus, and sulfur. In less significant, amounts, manganese, copper, titanium, sodium oxide, potassium oxide, fluorine, arsenic, and strontium may also occur.

rakesh61

Thanks Sir , Himanshu reading different books always confuses Same here

eistien

hey i too feel it is CaCO3 but could you tell me where you read it as gypsum???

spideyunlimited

if it was pure calcium carbonate it would be unfavourable for use as writing sticks!

madmax

Ya Pure chalk is extremely fragile and soft

rakesh61

from my edusys test series

Ask & Discuss Questions with Community & Experts