Tag: chemistry

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Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

State True or False.
Setting of cement is an endothermic process.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When water is mixed with cement to form a paste, reaction starts. In its pure form, the finely ground cement is extremely sensitive to water. Out of the three main compounds, $C _3A, C _3S \ and \ C _2S$, reacts quickly with water to produce a jelly-like compound which starts solidifying.


The action of changing from a fluid state to a solid state is called setting and should not be confused with hardening, which is a exothermic process.


So the statement is False.

Hence option B is correct.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Portland cement is manufactured by using:

  1. Limestone, clay and sand

  2. Limestone, gypsum and sand

  3. Limestone, gypsum and alumina

  4. Limestone, clay and gypsum
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Portland cement is the most common type of cement general use around the world, used as a basic ingredient of concrete mortar, stucco and most non-speciality grout. It developed from other types of hydraulic lime in England in the mid 19th century and usually originates from limestone. 


It is a fine powder produced by heating materials in a kiln to form what is called clinker, grinding the clinker, and adding small amounts of other materials. Several types of Portland cement are available with the most common being called ordinary Portland cement (OPC) which is grey in colour, but a white Portland cement is also available.

Portland cement is manufactured by using Limestone, clay and gypsum.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

The main constituent of cement is:

  1. $SiO _2$

  2. CaO
  3. $CaSO _4$
  4. $Al _2O _3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hydraulic cement are made up of a mixture of silicates and oxides in the form of silicon dioxide. It is responsible for the mechanical properties of cement.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

The main raw materials required for the manufacture of portland cement are:

  1. limestone and clay

  2. limestone and gpsum

  3. limestone and calcium chloride

  4. limestone and silica
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

It consists of calcium silicates and the ratio of calcium oxide to silicon dioxide is not less than 2. It consists of MgO not more than 5% by mass.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Which of the following is/are constituents of cement?

  1. $SiO _2$
  2. $Al _2O _3$
  3. $CaSO _4$

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Portland cement consists essentially of compounds of lime (calcium oxide, $CaO$) mixed with silica (silicon dioxide, $SiO _2$) and alumina (aluminum oxide, $Al _2O _3$). 

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

The main raw materials required for the manufacture of portland cement are:

  1. limestone and clay

  2. limestone and gypsum

  3. limestone and calcium chloride

  4. limestone and silica
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The raw materials needed to produce cement (calcium carbonate, silica, alumina and iron ore) are generally extracted from limestone rock, chalk, clayey schist or clay.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

A mixture of cement, gravel, coarse sand and water is called:

  1. mortar

  2. concrete

  3. slurry

  4. hardner
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Concrete is a building material that has high compressive strength and low tensile strength and is composed of a mixture of cement, gravel and sand (aggregates), and water.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Plaster of Paris is obtained by heating:

  1. gypsum

  2. limestone

  3. sodium carbonate

  4. calcium sulphate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Plaster of Paris is made by heating the mineral gypsum. When gypsum is heated to about 150°C it losses water and produces the powder of plaster of Paris.