Tag: some important compounds of magnesium and calcium

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Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Gypsum is added to cement clinker to:

  1. decrease the rate of setting of cement

  2. bind the particles of calcium silicate

  3. increase the tensile strength of the cement

  4. facilitate the formation of colloidal gel
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gypsum plays a very important role in controlling the rate of hardening of the cement. It slows sown the setting of cement so that cement is adequately hardened.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Calcium sulphate is found in nature in two forms, anhydrous calcium sulphate and hydrated calcium sulphate is heated with coke, sulphur dioxide gas is obtained. When hydrated calcium sulphate is heated at $200^oC$, it forms anhydrous salt.

When calcium sulphate is mixed with conc. $HCl$ and the paste is formed. What colour is obtained when a pinch of this paste is brought near the flame?

  1. golden yellow

  2. brick red

  3. crimson red

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

When calcium sulphate is mixed with conc. HCl the paste is formed. When this paste is brought near the flame, brick red colour is obtained which is the characteristic colour of calcium.


Golden yellow is the characteristic colour of sodium.

Crimnson red is the characteristic colour of strontium.

Apple green is the characteristic colour of barium.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Silica reacts with magnesium to form a magnesium compound $X$. $X$ reacts with dilute $HCl$ and forms $Y$.

  1. $MgO$
  2. $MgSiO _3$
  3. $SiCl _4$
  4. $MgCl _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
As per the given question reactions are:

$SiO _2+2Mg\rightarrow 2MgO+Si$
silica                          $X$

Again,

$MgO+2HCl\rightarrow MgCl _2+H _2O$
 $X$                                $Y$
Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Which among the following compound has the highest melting point?

  1. $\displaystyle C{ S } _{ 2 }$
  2. $\displaystyle HI$
  3. $\displaystyle { H } _{ 2 }S$
  4. $\displaystyle { H } _{ 2 }O$
  5. $\displaystyle MgO$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

$MgO$ has highest melting point, because this is ionic in character and has very high lattice energy.
Hence, the answer is $MgO$.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Among the following which is a white crystalline solid?

  1. $\displaystyle { C } _{ 3 }{ H } _{ 8 }$
  2. $\displaystyle CO$
  3. $\displaystyle Cu{ Cl } _{ 2 }$
  4. $\displaystyle { Cr } _{ 2 }{ O } _{ 3 }$
  5. $\displaystyle MgO$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Magnesium oxide (MgO) is a white, high-melting crystalline solid used in refractories.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

The reaction between a metal and a diatomic gas leads to an ionic substance. What is the formula unit of the ionic compound produced when magnesium reacts with hydrogen gas?

  1. $MgO$
  2. $Mg(OH) _2$
  3. $MgH _{2}$

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Magnesium react with hydrogen to produce magnesium hydride. chemical equations is as: 

$Mg + H _2 \rightarrow MgH _2$

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Which of the following represents the use(s) of Sorel's cement?

  1. It is used as a dental stopping

  2. It is used as finish for plaster

  3. It is used for cementing glass and metal together

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

The following represents the use(s) of Sorel's cement.

  1. It sets to a hard white mass. Hence, it is used as a dental stopping.
  2. It takes a very good polish and is used as a finish for plaster.
  3. It is used for cementing glass and metal together.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

When burned in open air, the magnesium gets hot enough to produce noticeable amounts of yellow magnesium nitride. Burning in a covered crucible that allows enough air in to support combustion will reduce the burning temperature, thus maximizing the production of the nitride.

  1. True

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

When magnesium burns, it is actually reacting with oxygen in the air and not with fire. Fire is what we call the heat and light produced when things burn Magnesium reacts with oxygen to make a compound called magnesium oxide. The bright light results because this reaction produces a lot of heat. so given statement is false