Chemistry

Chemical Reactions and Processes

626 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 substances in common use salts and their properties study of some important salts salts used in daily life

The metal whose hydroxide does not decompose on heating but its nitrate decomposes is:

  1. $Ca$
  2. $Al$
  3. $Na$
  4. $Fe$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$NaOH \xrightarrow {heat} $ no reaction
$NaNO _3 \xrightarrow {heat} NaNO _2+\frac{1}{2}O _2$

The metal whose hydroxide does not decompose on heating but its nitrate decomposes is sodium.

Multiple choice chemistry substances in common use salts and their properties study of some important salts salts used in daily life

Which one of the following products is formed when a mixture of steam, sulphur dioxide gas and oxygen gas (from air) is passed over dry lumps of common salt, the sodium chloride?

  1. $ Na _2SO _3 $
  2. $ Cl _3 $
  3. $ NaHSO _3 $
  4. $ Na _2SO _4 $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Hargreaves process:
$ 4NaCl (s) + 2SO _2 (g) + 2H _2O (g) + O _2 (g) \longrightarrow 2Na _2SO _4 + 4HCl $

Multiple choice bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

For the redox reaction:


          $Zn+N{ O }^- _3\rightarrow Zn^{2+}+NH^+ _4$ 

in a basic medium, coefficients of $Zn, \ NO^- _3$ and $OH^-$ in the balanced equation respectively are:

  1. $4, 1, 7$
  2. $7, 4, 1$
  3. $4, 1, 10$
  4. $1, 4, 10$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Balancing the redox reaction Zn + NO3- -> Zn2+ + NH4+ in basic medium involves balancing electrons and charge. The balanced equation is 4Zn + NO3- + 7H2O -> 4Zn2+ + NH4+ + 10OH-. Thus, the coefficients are 4, 1, and 10.

Multiple choice hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry
Unknown metal Appearance Reactions with dilute HCl Reaction with dilute HNO$ _3$
 (1) Dull gray solid with white oxide coating  Dissolved with bubbles of clear gas  Dissolved with bubbles of clear gas
 (2) Solid; lustrous smooth silver-gray surface No reaction  Dissolved with bubbles of orange gas

The addition of dilute HNO$ _3$ to unknown metal (2) produced an orange gas. Which of the following is the orange gas?

  1. Cl$ _2$
  2. H$ _2$
  3. O$ _2$
  4. CO$ _2$
  5. NO$ _2$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The addition of dilute $HNO _3$ to unknown metal (2) (silver metal) produced an orange gas nitrogen dioxide $\displaystyle (NO _2)$.
Note: Various gases have following colours.
$Cl _2-$ green
$H _2-$ colorless
$O _2-$ colorless
$CO _2-$ colorless
$NO _2-$ orange/brown

Multiple choice chemistry manmade materials synthetic rubber rubber polymer

A : A mixture of raw rubber and sulphur on heating at $373:K$ - $415:K$ gives vulcanised rubber.
R : ZnO decreases the rate of vulcanisation of rubber.

  1. both A and R are correct and R is the correct explanation of the A

  2. both A and R are correct but R is not the correct explanation of the A

  3. A is correct but R is incorrect

  4. A is incorrect but R is correct
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Natural rubber becomes soft at high temperature (>335 K) and brittle at low temperatures (<283 K) and shows high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. 

To improve upon these physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.

In sulfur vulcanization of natural rubber, the types of cross-links formed largely depend on the vulcanization system. The vulcanizing agents are zinc oxide (ZnO), stearic acid, accelerators, and sulfur. Conventional ZnO, or micro ZnO, is one of the basic components of rubber compounds and acts as an activator for rubber crosslinking by sulfur or sulfur donors.

Hence, reason given is incorrect. So, option C is correct.
Multiple choice chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

Which reagent, when mixed with ammonium sulfate and then heated, liberates ammonia?

  1. aqueous bromine

  2. dilute hydrochloric acid

  3. limewater

  4. potassium dichormate (VI) in acidic solution
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Test for the ammonium ion is adding a base then warming and then ammonia gas is produced therefore answer is C because limewater is $Ca(OH) _2$ which is a base and when it reacts with an ammonium ion which ammonium sulphate it produces ammonia gas overall reaction is:
$Ca(OH) _2 + (NH _4) _2SO _4 \rightarrow CaSO _4 + 2NH _3 + 2H _2O$
Multiple choice distinguish between black copper oxide and black manganese dioxide practical work chemistry

$CuO$ reacts with $HCl$ but $Cu$ does not, why?

  1. Copper has a higher reduction potential than hydrogen, it does not react with non-oxidising acids like $HCl$
  2. Copper has a lower reduction potential than hydrogen, it does not react with non-oxidising acids like $HCl$

  3. Copper is a least reactive metal hence does not react with any acid
  4. Both $Cu$ and $CuO$ does not react with $HCl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Copper does not react with $HCl$ acid, but copper oxide does react. Copper has a higher reduction potential than hydrogen, hence it does not react with non-oxidising acids like $HCl$ or dil.$H _2SO _4$.
But metal oxides are basic substances, and so they generally react with acids forming respective salt and water. 

Multiple choice distinguish between black copper oxide and black manganese dioxide practical work chemistry

Why should the reaction between manganese dioxide and hydrochloric acid carried out in a fume cupboard?

  1. Manganese causes skin irritations

  2. Both reactants and products causes itching

  3. Chlorine gas is poisonous

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

When manganese dioxide is treated with hydrochloric acid, chlorine gas is released as a product which can be poisonous. Hence, the procedure should take place in a fume cupboard to prevent any harmful effects.

Multiple choice distinguish between black copper oxide and black manganese dioxide practical work chemistry

The reaction between copper oxide and hydrochloric acid is a:

  1. acid base reaction

  2. replacement reaction

  3. combustion reaction
  4. both $A$ and $B$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The reaction copper oxide and hydrochloric acid is an acid-base reaction due to the hydrogen and oxygen found in the reactants, then forming water ($H _2O$). This is also a replacement reaction because the copper ($Cu$) is "swapping out" with the hydrogen ($H$) creating two different molecules.