Tag: practical work

Questions Related to practical work

$\displaystyle \underset {orange}{Cr _2O _7^{2-}}\,\overset {pH=x}{ \underset {pH = y}{\leftrightarrows}}\, \underset {green}{CrO _4^{2-}}$. 


This change is based on change in pH. 

Find values of x and y  :

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. $8, 6$

  2. $8, 10$

  3. $4, 6$

  4. change is independent of pH

Show answer
Correct Option: A
Explanation:

The process involves the equilibrium between chromate (VI), dichromate (VI) and hydrogen ions:


$2{ Cr{ O } _{ 4 }^{ 2- } } _{ \left( aq. \right)  \left( yellow \right)  }+2{ { H }^{ + } } _{ \left( aq. \right)  }\rightleftharpoons { { Cr } _{ 2 }{ O } _{ 7 }^{ 2- } } _{ \left( aq. \right)  \left( orange \right)  }+{ { H } _{ 2 }O } _{ \left( l \right)  }$

The addition of acid encourages the equilibrium towards the right (pH=6), producing more orange colored dichromate (VI) ions. The addition of hydroxide ions causes the concentration of hydrogen ions to decrease, and this brings the equilibrium back to the left-hand side, regenerating yellow chromate (VI) ions.

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

Which of the following represents unknown metal (2) ?

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. Carbon

  2. Copper

  3. Zinc

  4. Sodium

  5. Silver

Show answer
Correct Option: E
Explanation:

Unknown metal (2) could be silver. It is a relatively inert metal. 
Note: Carbon is not a metal. Copper is brownish, zinc is reactive metal with whitish oxide coat in air. Sodium is highly reactive and explodes when it comes in contact with water. It reacts with acids even violently.

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 transparent gas is produced by the addition of dilute HCI to unknown metal (1). Which of the following represents the transparent gas ?  

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. Cl$ _2$

  2. H$ _2$

  3. O$ _2$

  4. CO$ _2$

  5. NO$ _2$

Show answer
Correct Option: B
Explanation:

When dilute $HCl$ is added to the unknown metal  (1) (zinc), the transparent gas produced is hydrogen. 
Note: Chlorine and $NO _2$ gases are green and orange coloured respectively. $CO _2$ is not possible as no $C$ atoms are present.
Also, metals react with acids to form hydrogen gas.

pH scale ranges from :

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. $1-15$

  2. $0-14$

  3. $1-20$

  4. none of the above

Show answer
Correct Option: B
Explanation:

The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic.

What can be used to measure the strength of acidity or basicity of a solution?

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. Litmus paper

  2. pH meter

  3. Both $A$ and $B$

  4. None of the above

Show answer
Correct Option: B
Explanation:

The pH meter is a device used for measuring ph, which is either the concentration or the activity of hydrogen ions in an aqueous solution. It usually has a glass electrode plus a calomel reference electrode or a combination of an electrode.

What is pH?

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. Used in identification of cations

  2. Identification of non metals

  3. Specify the acidity or basicity of an aqueous solution

  4. Both $A$ and $C$

Show answer
Correct Option: C
Explanation:

$pH$ is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is roughly the negative of the logarithm to base 10 of the concentration, measured in units of moles per liter, of hydrogen ions or $H^+$.

The use of pH is in :

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. soil analysis

  2. water analysis

  3. medical field

  4. all of the above

Show answer
Correct Option: D
Explanation:

The use of pH is in soil analysis to test whether the soli is acidic or basic, water analysis to test whether water is pure or not and medical field to calculate the pH of blood, urine samples.

The scale showing the relative strength of the acids and alkalis is known as :

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. acid scale

  2. basic scale

  3. pH scale

  4. alkaline scale

Show answer
Correct Option: C
Explanation:

The scale showing the relative strength of the acids and alkalis is known as pH scale.

pH of soil varies from :

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. $2-4$

  2. $3-9$

  3. $4-8$

  4. $3-5$

Show answer
Correct Option: B
Explanation:

pH of soil generally varies from $3$ to $9$.

pH of clear rain water varies from :

hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

  1. $3-4$

  2. $4-5$

  3. $5.5-6$

  4. $6.5-7$

Show answer
Correct Option: C
Explanation:

pH of clear rain water varies from $5.5$ to $6$.