Chemistry

Chemical Reactions and Processes

571 Questions

Chemical reactions and processes questions cover the transformation of substances through electrolysis, thermal decomposition, and catalysis. Key areas include identifying gas evolution, balancing chemical equations, and understanding industrial chemical applications. This general chemistry topic is a staple in the science sections of multiple competitive examinations.

Thermal decompositionElectrolysis processGas evolution reactionsHeterogeneous catalystsFuel cell components

Chemical Reactions and Processes Questions

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

A metal $M$ does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify black coloured product is:

  1. $MgO$
  2. $CuO$
  3. $FeO$
  4. $ZnO$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The metal $M$ is copper $(Cu)$ which reacts with oxygen when heated in the air to form black coloured copper(ll) oxide. The reaction can be written as:
$2Cu + O _{2} \rightarrow 2CuO$

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

The gaseous product formed when magnesium reacts with boiling water is :

  1. hydrogen

  2. washing soda

  3. sulphurous

  4. calcium oxide
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hydrogen gas is formed when magnesium reacts with water to form its hydroxide as Mg is highly reactive with water and acids. It is present on the top of the activity series. So, it is a very reactive metal.

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

On reaction with water, an active metal produces:

  1. oxygen

  2. nitric acid

  3. base

  4. metal hydroxide

  5. none of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The reactivity of active metals can be demonstrated by dropping pieces of $Li, Na, K$ into water. $Li$ reacts slowly with water, $Na$ reacts more rapidly and $K$ reacts violently. For a reaction between sodium and water, it can be divided into two halves. One-half reaction describes what happens when sodium atoms lose electrons. The other half describes what happens when water molecules gain these electrons. An overall equation is obtained for the reaction which shows the formation of metal hydroxide and evolution of hydrogen gas.
$2Na\left( s \right) +2{ H } _{ 2 }O\left( l \right) \rightarrow 2{ Na }^{ + }\left( aq \right) +2{ OH }^{ - }\left( aq \right) +{ H } _{ 2 }\left( g \right) \uparrow $

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

What happens when water vapour is passed over a red hot iron?

  1. No reaction
  2. Oxygen and $Fe{(OH)} _{2}$ are produced
  3. Hydrogen and ${Fe} _{2}{O} _{3}$ are produced
  4. Hydrogen and ${Fe} _{3}{O} _{4}$ are produced
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The reaction takes place as

$3Fe + 4H _2O \rightarrow Fe _3O _4 + 4H _2$
so, on passing water vapour over hot red iron we get hydrogen and $Fe _3O _4$.

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

A silvery-white metal $X$ reacts with water at room temperature to produce a water-soluble compound $Y$ and a colourless gas $Z$. The reaction is highly exothermic and the $Z$ catches fire immediately during the reaction. The solution of $Y$ in the water on reacting with a stoichiometric amount of dilute solution of hydrochloric acid gives a solution of $pH = 7.0$. 
The compounds $X,\ Y$ and $Z$ respectively are:

  1. $Al,Al(OH) _3 $ and $ H _2$
  2. Ag, AgOH and $H _2$
  3. K, KCl and $H _2$
  4. Na, NaOH and $H _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$2Na+H _2O\rightarrow 2NaOH+H _2+Heat$

$NaOH+HCl\rightarrow NaCl+H _2O$
$X,\ Y,\ Z$ are $Na$, $NaOH$, $H _2$

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

Aluminium does not react with water at room temperature because:

  1. it is above hydrogen in the activity series

  2. it is below hydrogen in the activity series
  3. it is covered with a thin film of $AlN$
  4. it is covered with thin film of $Al _2O _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Aluminium is oxidized by water at temperatures below $280^oC$  to produce hydrogen, aluminium hydroxide and heat. The challenge in this reaction is circumventing the formed oxide layer which inhibits the reaction and the expenses associated with the storage of energy by regeneration of $Al$ metal.

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

What happens when steam is passed over red hot iron?

  1. No reaction takes place.
  2. $O _2$ and $Fe(OH) _2$ are formed.
  3. $H _2$ and $Fe _3O _4$ are formed.
  4. $H _2$ and $Fe _2O _3$ are formed.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When steam is passed over red hot iron, $H _2$ and $Fe _3O _4$ are formed. The reaction is as follows:
$3Fe+4{ H } _{ 2 }O\rightarrow { Fe } _{ 3 }{ O } _{ 4 }+4{ H } _{ 2 }\uparrow $

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

When a small piece of dry sodium is put in water, it reacts vigorously to produce:

  1. nitrogen gas

  2. hydrogen gas

  3. carbon dioxide gas

  4. sulphur dioxide
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Most of the metals do not react with water. However,alkali metals react vigorously with water. Reaction of sodium metal with water: Sodium metal forms sodium hydroxide and liberates hydrogen gas along with lot of heat when reacts with water.
 When sodium reacts with water, sodium hydroxide is formed hydrogen gas as a byproduct that gets burnt with a bright flame making the reaction highly exothermic.
  
Multiple choice chemistry metals reaction of metals reactions of metals chemical properties of metals

The incorrect statement among the following for magnesium metal is:

  1. it burns in oxygen with dazzling white flame

  2. tt reacts with cold water to form magnesium oxide and evolves hydrogen gas

  3. it reacts with hot water to form magnesium hydroxide and evolves hydrogen gas

  4. it reacts with steams to form magnesium hydroxide and evolves hydrogen gas
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Magnesium burns in steam to produce white magnesium oxide and hydrogen gas. If a metal reacts with cold water the metal hydroxide is formed but if it reacts with steam the metal oxide is formed.

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

In case of reaction between sodium and cold water, hydrogen burns with _______ flame, whereas, in case of reaction between potassium and cold water, hydrogen burns with _____ color.

  1. Yellow, lilac

  2. Orange, yellow

  3. Orange, lilac

  4. Lilac, yellow
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When sodium is added to water, the sodium melts to form a ball that moves around on the surface. It fizzes rapidly, and the hydrogen produced may burn with an orange flame before the sodium disappears.When potassium is added to water, the metal melts and floats. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame.