Tag: some important compounds of magnesium and calcium

Questions Related to some important compounds of magnesium and calcium

Gypsum is added to cement clinker to:

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

  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

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Correct Option: A
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.

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?

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

  1. golden yellow

  2. brick red

  3. crimson red

  4. apple green

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Correct Option: B
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.

Which of the following is known as dead burnt?

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

  1. Gypsum

  2. Plaster of affairs

  3. Anhydrite

  4. None of these

Show answer
Correct Option: C

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

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

  1. $MgO$

  2. $MgSiO _3$

  3. $SiCl _4$

  4. $MgCl _2$

Show answer
Correct Option: D
Explanation:
As per the given question reactions are:

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

Again,

$MgO+2HCl\rightarrow MgCl _2+H _2O$
 $X$                                $Y$

Which among the following compound has the highest melting point?

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

  1. $\displaystyle C{ S } _{ 2 }$

  2. $\displaystyle HI$

  3. $\displaystyle { H } _{ 2 }S$

  4. $\displaystyle { H } _{ 2 }O$

  5. $\displaystyle MgO$

Show answer
Correct Option: E
Explanation:

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

Among the following which is a white crystalline solid?

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

  1. $\displaystyle { C } _{ 3 }{ H } _{ 8 }$

  2. $\displaystyle CO$

  3. $\displaystyle Cu{ Cl } _{ 2 }$

  4. $\displaystyle { Cr } _{ 2 }{ O } _{ 3 }$

  5. $\displaystyle MgO$

Show answer
Correct Option: E

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?

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

  1. $MgO$

  2. $Mg(OH) _2$

  3. $MgH _{2}$

  4. None of these

Show answer
Correct Option: C
Explanation:

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

$Mg + H _2 \rightarrow MgH _2$

Which of the following is/are tue about $MgCl _2$?

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

  1. It is colourless.

  2. It is crystalline.

  3. It is deliquescent solid.

  4. All of the above

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Correct Option: D
Explanation:

$MgCl _2$ is colourless, crystalline, deliquescent solid which is highly soluble in water.

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

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

  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

Show answer
Correct Option: D
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.

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.

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

  1. True

  2. False

Show answer
Correct Option: B
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