Tag: chemistry

Questions Related to chemistry

$Mg+O _2\rightarrow\ ?$

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

  1. $MgO$

  2. $MgO+O _2$

  3. $2MgO+O _2$

  4. none of the above

Show answer
Correct Option: A
Explanation:

The reaction between Mg and oxygen is as follow:

$2Mg+O _2\rightarrow\ 2MgO$

The tribasic form of calcium phosphate is ________ in water.

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

  1. soluble

  2. insoluble

  3. sparingly soluble

  4. soluble only at high temperature

Show answer
Correct Option: B
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.

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

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

  1. evolution of chlorine containing gases

  2. evolution of fluorine containing gases

  3. evolution of sulphur containing gases

  4. evolution of nitrogen containing gases

Show answer
Correct Option: B
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.

Gypsum is found in mainly which kind of rocks?

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

  1. Igneous

  2. Sedimentary

  3. Metamorphic

  4. All of these

Show answer
Correct Option: B
Explanation:

Gypsum or Calcium Sulphate dihydrate $CaSO _4.2H _2O$ is mostly found in beds of sedimentary rocks.

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

Show answer
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.