Chemistry

Chemical Compounds and Reactions

329 Questions

Chemical compounds and reactions involve understanding the properties, colors, and formation of various chemical substances. Questions focus on identifying precipitates, observing color changes during reactions, and naming common compounds. This topic is a fundamental part of the chemistry syllabus for competitive exams.

identifying precipitateschemical reaction colorscompound namingcolloidal particle propertiesacid base reactions

Chemical Compounds and Reactions Questions

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

Beryllium is placed above magnesium in the group II. Beryllium dust, therefore, when added to $MgCl {2}$ solution will ____________.

  1. have no effect

  2. precipitate Mg metal

  3. precipitate MgO

  4. lead to dissolution of Be metal
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Beryllium is less reactive than magnesium and cannot displace magnesium from its salts. In fact, magnesium is more electropositive than beryllium.

Multiple choice chemistry metals chemical properties and uses of metals and non-metals introduction to metals physical properties of non-metals

A fire work gave bright crimson light. It probably contained a salt of ____________.

  1. Ca

  2. Sr

  3. Ba

  4. Mg
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Strontium element gives crimson red flame and it may be the salt of strontium carbonate which is used in the manufacture of red fireworks and pure strontium is used in the study of neurotransmitter release in neurons.

Multiple choice chemistry chemistry in everyday life metal oxides and non metal oxides reactions of acids and bases properties of acids and bases

'The blue-green colour of the solution is due to the formation of copper(II) chloride in the reaction' is an example of which kind of chemical reaction?

  1. Reaction of metallic oxides with acids

  2. Reaction of non-metallic oxides with acids

  3. Reaction of metallic oxides with bases

  4. Reaction of non-metallic oxides with base
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Metal oxides always reacts with acid to form salt and water. Copper oxide when reacts with $HCl$ it forms blue-green copper(II) chloride. 

$2CuO + 2HCl \rightarrow 2CuCl _2 + H _2O$

Multiple choice chemistry chemistry in everyday life metal oxides and non metal oxides reactions of acids and bases properties of acids and bases

The black color of copper oxide turns blue on treating with $HCl$ because of:

  1. formation of cupric chloride

  2. formation of water

  3. release of hydrogen

  4. release of carbon dioxide
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When $HCl$ reacts with copper oxide, the black color of copper oxide turns blue due to formation of its corresponding salt i.e. calcium chloride. Water is formed along with salt.

Multiple choice chemistry chemistry in everyday life metal oxides and non metal oxides reactions of acids and bases properties of acids and bases

Black copper (II) oxide dissolves in colourless sulfuric acid to give:

  1. yellow solution of copper (II) sulfate

  2. blue solution of copper (II) sulfuric acid

  3. blue solution of copper (II) sulfate

  4. none of above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Cu(II) oxide\longrightarrow CuO$


$CuO+ H _2SO _4\longrightarrow \underbrace{CuSO _4} _{(Blue\quad coloured)}+H _2O$

Copper(II) oxide, a black solid and colourless dilute sulfuric acid react to produce copper(II) sulfate, giving a characteristic blue colour to the solution.

Hence, the corret option is $C$

Multiple choice chemistry metals reaction of metals reactions of metals chemical properties of metals

A reddish brown colored element $X$ on heating in air, becomes a black colored compound $Y$.  The compound $X$ and $Y$ are :

  1. $Cu, CuO$
  2. $Pb, PbO$
  3. $Fe, Fe _2O _3$
  4. $Cr, Cr _2O _3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$X$ is copper $(Cu)$ and the black-coloured compound formed is copper oxide $(CuO)$. The equation of the reaction involved on heating copper in given below.

$2Cu + O _{2} \rightarrow 2CuO$.
All other elements that are given are not black in colour

$Pb$ is grey in colour.
$Fe$ is silver-grey.
$Cr$ is steely-grey.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds
The Alsatian-Swiss chemist Alfred Werner pioneered the field of coordination chemistry in the late nineteenth century. At that time, a number of compounds of cobalt (III) chloride with ammonia were known, with general formula $CoCl _3.xNH _3$ $x=3\ to\ 6$
Treatment of these compounds with aqueous HCl acid did not remove the ammonia. However, treatment of the compounds with excess of $AgNO _3$ at 273 K gave white precipitate of AgCl in varying ratio depending on the structure. Also each complex had electrical conductivity of varying nature.
 
There is no reaction of the compound with aqueous HCl indicating that there is no free $NH _3$. Thus, $NH _3$ ligand is bonded to cobalt(III) by________ .

  1. Primary valency.

  2. Secondary valency.

  3. Both of these.

  4. None of these.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Option (B) is correct.

Thus, $NH _3$ ligand is bonded to cobalt$(III)$ by secondary valency. Ammonia is present inside the coordination sphere and does not ionises while chloride ions present outside the sphere reacts with $AgNO _3$

$[Co(NH _3) _5Cl]Cl _2 + AgNO _3 \longrightarrow [Co(NH _3) _5Cl](NO _3) _2 + AgCl _2$
Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

When $AgNO _3$ is added to a solution of $Co(NH _3) _5 Cl _3$, the precipitate of $AgCl$ shows two ionized chloride ions. This means:

  1. only two chlorine atoms satisfy primary valency and one secondary valency

  2. one chlorine atom satisfies primary as well as secondary valency

  3. two chlorine atoms satisfy primary valency

  4. three chlorine atoms satisfy secondary valency
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

Option (B),(C) are correct.
When $AgNO _3$ is added to a solution of $Co(NH _3) _5 Cl _3$, the precipitate of $AgCl$ shows two ionized chloride ions.This means one chlorine atom satisfies primary as well as secondary valency and two chlorine atoms satisfy primary valency. Hence, $Co(NH _3) _5 Cl _3$, can be written as $[Co(NH _3) _5 Cl]Cl _2$,

Multiple choice dyes dyes and pigments chemistry in daily life applied chemistry chemistry

Match metal ion (Part I) with colour (Part II) in presence of alizarin:


  Part I   Part II
I. ${ Sn }^{ 2+ }$ A. Blue
II. ${ Mg }^{ 2+ }$ B. Pink
III. ${ Al }^{ 3+ }$ C. Violet
IV. ${ Ba }^{ 2+ }$ D. Red

  1. I-A II-D III-C IV-B

  2. I-B II-A III-D IV-C

  3. I-C II-B III-A IV-D

  4. I-D II-C III-B IV-A
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
$Alizarin$ is a typical mordant dye gives different colours with metal ions as some of them are given below: 

$Al^{3+} \Rightarrow Red$
$Sn^{2+}  \Rightarrow Pink$
$Ba^{2+} \Rightarrow Voilet$
$Mg^{2+} \Rightarrow Blue$

Option B is correct.