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

The tribasic form of calcium phosphate is ________ in water.

  1. soluble

  2. insoluble

  3. sparingly soluble

  4. soluble only at high temperature
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Tricalcium phosphate (TCP) is a calcium salt of phosphoric acid with the chemical formula $Ca _3(PO _4) _2$. It is also known as tribasic calcium phosphate and bone phosphate of lime (BPL). It is a white solid, with very low solubility.

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

The major problem in the production of single superphosphate(SSP) is:

  1. evolution of chlorine containing gases

  2. evolution of fluorine containing gases

  3. evolution of sulphur containing gases

  4. evolution of nitrogen containing gases
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The evolution of fluorine containing gases is a major problem in the SSP production process. Theese gases arise from the fluoride and silicon contained as impurities in the rock. These elements combine with the water to form flurosilic acid$ (H _2SiF _6). $ Any excess silicon dissolves (in acid) to form silicic acid $(SiO _2-H _2O).$Typical rock phosphate contains about 8% Silica and 3% Fluorine by weight.

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

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

  1. Monobasic form

  2. Tribasic form

  3. Both

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

How is Calcium Sulphate produced from Calcium Oxide?

  1. $CaO$ $+$ $H _2SO _4$
  2. $CaO$ $+$ $SO _2$
  3. $CaO$ $+$ $SO _3$
  4. $CaO$ $+$ $S$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

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

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

  1. $CaSO _4,xH _2O$
  2. $BaSO _4,xH _2O$
  3. $MgSO _4,xH _2O$

  4. All have the same value of x
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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

  1. $CaSO _4$
  2. $CaSO _4.\frac{1}{2}H _2O$
  3. $CaSO _4.H _2O$
  4. $CaSO _4.2H _2O$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

Gypsum is added to cement to:

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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.