Thoria is an expensive refractory material and is radioactive in nature. Thorium oxide is used in the manufacture of

An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture?

A

Cork

B

Saw dust

C

Sand

D

Chemically prepared foam

What is Thoria?

A

Thoria Has high fusion temperature (> 3000°C) but poor resistance to thermal shock

B

Thoria Has high resistance to basic slags

C

Which is expensive & radioactive, is used in crucibles for melting high purity metals

D

All of the above

Dry mix hydraulic compositions of refractory aggregates with suitable bonding materials are called refractory

A

Mortars

B

Cements

C

Castables

D

None of these

If a refractory contains high content of silicon, it means refractory is

A

Acidic

B

Basic

C

Neutral

D

Brittle

240 radioactive grams of goo loses half its radioactivity every 10 days. How many grams of radioactive goo is left in 40 days?

A

120

B

60

C

15

D

none

The half life period of a radioactive substance is best determined by counting the number of alpha particles emitted per second in a Geiger Muller counter from its known quantity. If the half life period of a radioactive substance is one month, then

A

$${\frac{3}{4}^{{\text{th}}}}$$ of it will disintegrate in two months

B

It will completely disintegrate in two months

C

It will completely disintegrate in four months

D

$${\frac{l}{8}^{{\text{th}}}}$$ of it will remain intact at the end of four months

Alumina, silica, lime and iron oxide are the basic raw material for the manufacture of portland cement. The component of Portland cement which first hardens is

A

5CaO . 3Al₂O₃

B

3CaO . Al₂O₃

C

3CaO . SiO₂

D

2CaO . SiO₂

Which catalyst is used in the manufacture of ethylene oxide by oxidation of ethylene?

A

AgO

B

Al₂O₃

C

ZnCl₂

D

FE₂O₃

নিম্নের কোন oxide টিকে উভধর্মী oxide বলে?

A

CaO

B

MgO

C

ZnO

D

CuO

Which metal oxide is an amphoteric oxide?

A

iron

B

aluminium

C

sodium

D

potassium

Thoria is an expensive refractory material and is radioactive in nature. Thorium oxide is used in the manufacture of

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