Tag: chemistry

Questions Related to chemistry

Calcining at different temperatures produces magnesium oxide of different reactivity.

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

  1. True

  2. False

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Correct Option: A
Explanation:

Calcining at different temperatures produces magnesium oxide of different reactivity.

High temperatures (1500 – 2000 °C) diminish the available surface area and produces dead-burned (often called dead burnt) magnesia, an unreactive form used as a refractory.
Calcining temperatures (1000 – 1500 °C) produces hard-burned magnesia, which has limited reactivity and calcining at lower temperature, (700 – 1000 °C) produces light-burned magnesia, a reactive form, also known as caustic calcined magnesia.
Although some decomposition of the carbonate to oxide occurs at temperatures below 700 °C, the resulting material appears to reabsorb carbon dioxide from the air.

Which of the following alkali earth metal(s) form ionic oxide?

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

  1. $BeO$

  2. $MgO$

  3. $CaO$

  4. $SrO$

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Correct Option: B,C,D
Explanation:

$BeO$ forms amphoteric oxide because it acts as both acidic oxide as well as basic oxide. $MgO,CaO,SrO$ are ionic oxide.

Which of the following is not a method of production of magnesium oxide?

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

  1. $ Mg+O _2 \rightarrow MgO $

  2. $MgCO _3\xrightarrow{\Delta}MgO+CO _2$

  3. $Mg(OH) _2\xrightarrow{\Delta}MgO+H _2O$

  4. None of the above

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Correct Option: D
Explanation:

All of the above methods are used for the production of magnesium oxide.when magnesium is burnt in air magnesium oxide is produced. When magnesium carbonate is calcined magnesium oxide and carbon dioxide is produced. When magnesium hydroxide is calcined magnesium oxide and water is produced.

Magnesium oxide is not used in:

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

  1. refractive industry

  2. medicine

  3. construction

  4. none of these

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Correct Option: D
Explanation:
Option $(D)$ is correct.
Magnesium oxide is a mineral supplement used to treat or prevent low levels of magnesium in the blood. Magnesium is important for many systems in the body, but it is especially vital for healthy muscles and bones. Some people use it as an antacid to relieve heartburn, sour stomach, or acid indigestion. It also may be used as a laxative for short-term, rapid emptying of the bowel. It  is available without a prescription.

Give chemical name and nature (acidic or basic) of the ash formed by burning of a $Mg$ ribbon in the air? 

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

  1. magnesium chloride, acidic

  2. magnesium nitrite, basic

  3. magnesium oxide, acidic

  4. magnesium oxide, basic

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Correct Option: D
Explanation:
Option $(D)$ is correct.
Magnesium oxide is formed as ash by burning of $Mg$ ribbon in the air. This is an exothermic reaction.
$2Mg + O _2 \rightarrow 2MgO + \:energy$
Magnesium oxide is basic in nature as it reacts with water to form magnesium hydroxide which is a base.

Oxide used to treat indigestion and relieve pain is:

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

  1. magnesium hydroxide

  2. magnesium oxide

  3. calcium oxide

  4. both $A$ and $B$

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Correct Option: D
Explanation:
Option $(D)$ is correct.
Oxide used to treat indigestion and relieve pain are magnesium hydroxide and magnesium oxide. Heartburn and acid indigestion are caused by excess acid in the stomach. Magnesium oxide and hydroxide treats these stomach problems by neutralizing the acid in the stomach. 

The powder of zinc phosphate cement contain zinc oxide and:

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

  1. magnesium sulphate

  2. magnesium phosphate

  3. magnesium oxalate

  4. magnesium oxide

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Correct Option: D
Explanation:
Option $(D)$ is correct.
The powder of zinc phosphate cement contains zinc oxide and magnesium oxide. It is used for dentistry, cementation of inlays, crowns, bridges etc.

The compounds of alkaline earth metals ($Mg$) have following magnetic nature:

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

  1. diamagnetic

  2. anti ferromagnetic

  3. ferromagnetic

  4. paramagnetic

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Correct Option: A
Explanation:

The compounds of alkaline earth metal are diamagnetic because they don't have any unpaired electrons. Their electronic configuration is $np^6ns^2$.

Which of the following(s) is/are correct for magnesium and zinc?

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

  1. $MgO$ and $ZnO$ are amphoteric

  2. $MgCO _3$ and $ZnCO _3 $ both on heating give corresponding oxides

  3. Both are used as electrodes

  4. Both are used to prevent corrosion

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Correct Option: B,C,D
Explanation:
Option $(B)\ ,(C),\ (D)$ are correct. They all are facts.
$MgO$ is basic while $ZnO$ is amphoteric in nature.

Magnesium is an important component of which biomolecule occuring extensively in living world?

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

  1. Haemoglobin

  2. ATP

  3. Chlorophyll

  4. Vitamin B

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Correct Option: C
Explanation:

Hemoglobin contains iron, vitamin $B$, cobalt. Chlorophyll contains magnesium. ATP is adenosine triphosphate contains phosphorous.