Tag: some important compounds of magnesium and calcium

Questions Related to some important compounds of magnesium and calcium

Which of the following form is the soluble form of calcium phosphate?

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

  1. Monobasic form

  2. Tribasic form

  3. Both

  4. None

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Correct Option: A
Explanation:

Monocalcium phosphate is an inorganic compound with the formula $Ca{(H _2PO _4)} _2$. It is commonly found as the monohydrate $Ca{(H _2PO _4)} _2.H _2O$. Both salts are colourless solids. They are used mainly as water soluble superphosphate fertilisers.

How is Calcium Sulphate produced from Calcium Oxide?

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

  1. $CaO$ $+$ $H _2SO _4$

  2. $CaO$ $+$ $SO _2$

  3. $CaO$ $+$ $SO _3$

  4. $CaO$ $+$ $S$

Show answer
Correct Option: A
Explanation:

Calcium sulphate can be produced from Calcium oxide by reacting it with Sulphuric acid. The reaction can be written as-
$CaO$ $+$ $H _2SO _4$ $=$ $CaSO _4$ $+$ $H _2O$

Formula of Epsom salt is:

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

  1. $MgCO _{3}$

  2. $MgSO _{4}$

  3. $MgSO _{4} . 7H _{2}O$

  4. $MgSO _{4} . 6H _{2}O$

Show answer
Correct Option: C
Explanation:

The correct formula of Epsom salt is ${ MgSO } _{ 4 }\cdot { 7H } _{ 2 }O$. 

In which of following cases is the value of x maximum?

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

  1. $CaSO _4,xH _2O$

  2. $BaSO _4,xH _2O$

  3. $MgSO _4,xH _2O$

  4. All have the same value of x

Show answer
Correct Option: C
Explanation:

$MgSO _4$ has 7 moles of water of hydration.
$CaSO _4$ has 2 moles of water hydration $BaSO _4$ has 1 mole of water of hydration.
Thus $MgSO _4$ has maximum x.

Choose the correct answer from the alternatives given.
Dead burnt plaster is :

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

  1. $CaSO _4$

  2. $CaSO _4.\frac{1}{2}H _2O$

  3. $CaSO _4.H _2O$

  4. $CaSO _4.2H _2O$

Show answer
Correct Option: A
Explanation:

Anhydrous calcium sulphate, CaSO$ _4$ is known as 'dead burnt plaster'. It is formed by heating gypsum, $CaSO _4.2H _2O$ at a temperature above 393 K.

Gypsum is added to cement to:

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

  1. make the mixture more homogeneous

  2. improve the texture of cement

  3. make the cement light weight

  4. delay the setting time of cement

Show answer
Correct Option: D
Explanation:

The purpose of adding gypsum is only to slow down the process of setting of the cement so that it gets sufficiently hardened.

Hence, gypsum is added to cement to delay the setting time of cement.

Which of the following compounds is known as epsom salt ?

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

  1. $CaSO _{4}.2H _{2}O$

  2. $MgSO _{4}.7H _{2}O$

  3. $FeSO _{4}.7H _{2}O$

  4. $Mg _{3}(PO _{4}) _{2}$

Show answer
Correct Option: B
Explanation:

$Mg{ SO } _{ 4 }\cdot 7{ H } _{ 2 }O$ is also known as Epsom salt.

Gypsum on heating to $300^{o}C$ gives:

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

  1. $CaSO _{4}2H _{2}O$

  2. $CaSO _{4}$

  3. $CaSO _{4}.\dfrac {1}{2}H _{2}O$

  4. $SO _{3}$ ans $CaO$

Show answer
Correct Option: C
Explanation:

Here answer is option C

Gypsum- chemical formula ;$Ca{ SO } _{ 4 }\cdot 2{ H } _{ 2 }O$
When gypsum is heated at 300K, we get plaster of paris(calcium sulphate hemihydrated salt)
$Ca{ SO } _{ 4 }\cdot 2{ H } _{ 2 }O\rightarrow Ca{ SO } _{ 4 }\frac { 1 }{ 2 } { H } _{ 2 }O+\frac { 3 }{ 2 } { H } _{ 2 }O$
Hence calcium sulphate Hemihydrated salt $Ca{ SO } _{ 4 }\frac { 1 }{ 2 } { H } _{ 2 }O$ is produced after heating gypsum.

$30\ g$ of Magnesium and $30\ g$ of oxygen are reacted, then the residual mixture contains:

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

  1. $50\ g$ of Magnesium oxide and $10\ g$ of oxygen

  2. $40\ g$ of Magnesium oxide and $20\ g$ of oxygen

  3. $45\ g$ of Magnesium oxide and $15\ g$ of oxygen

  4. $50\ g$ of Magnesium only

Show answer
Correct Option: A
Explanation:
$2Mg+ { O } _{ 2 } \rightarrow 2 MgO$
According to the above reaction,
$28.6 g (2 mole)\ Mg$ combine with $32 g (1mole)$ of ${ O } _{ 2 }$ to give $80.6g(2mole)$ of MgO.
thus,
$30 g\ Mg$ will combine with $20 g$ of ${ O } _{ 2 }$ to produce $50 g\ MgO$ and $10 g$ ${ O } _{ 2 }$will remain unreactive.

About $2.5\%$ gypsum $(CaSO _{4}.H _{2}O)$ is also added to cement as one of the consituents its function is to:

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

  1. Slow down the setting process to increase strength

  2. Speed the setting process to increase strength

  3. Absord moisture

  4. Make it anti-rusting

Show answer
Correct Option: A
Explanation:

Gypsum is a mineral and is hydrated calcium sulphate in chemical form. Gypsum plays a very important role in controlling the rate of hardening of the cement. During the cement manufacturing process, upon the cooling of clinker, a small amount of gypsum is introduced during the final grinding process.Gypsum is added to control the “setting of cement”. If not added, the cement will set immediately after mixing of water leaving no time for concrete placing.
conclusion: hence the option (A) is correct