Acids Bases and Salts MCQ Quiz - Objective Question with Answer for Acids Bases and Salts - Download Free PDF

Concept:

• Oxides are compounds formed by the reaction of metals, non-metals with oxygen.

The types of oxides are:

• Basic oxide: It is a complex chemical substance oxide, which forms a salt with a chemical reaction with acids or acidic oxides and does not react with bases or basic oxides.
• E.g. Copper oxide (Cu2O), Magnesium oxide (MgO)
• Acidic oxide: It is a complex chemical substance oxide, which forms a salt with the chemical reactions with bases or basic oxides and does not react with acidic oxides.
• E.g. Carbon dioxide (CO2), Silicon dioxide (SiO2)
• Amphoteric oxide: It is a complex chemical substance, also oxides, which form a salt with the chemical reactions with acids (or acid oxides) and with bases (or basic oxides).
• E.g. Copper, Zinc, Tin, Lead, Aluminum, and Beryllium.

Explanation:

Nature of Oxides

• Oxides of non - metals are acidic in nature. 
• In an aqueous solution, they will behave as acid and turn blue litmus to red. 
• The aqueous solution of a metallic oxide is basic in nature. 
• In an aqueous solution, they will behave as a base as turn red litmus to blue.

Important Points

Basic Knowledge: Metal oxides are basic in nature and non-metallic oxides are acidic in nature.

The correct answer is Salt, water and heat

Explanation:

• Acids are substances that dissolve in water to form H⁺ ions, whereas bases are substances that dissolve in water to form OH⁻ ions.
• When an acid reacts with a base, salt, and water are formed. 
• For example, When hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) base to form sodium chloride (NaCl) salt and water (H₂O). 
• Example:

NaOH + HCl → NaCl + H₂O + Heat

• The reaction of an acid with a base is called a neutralization reaction.
• In neutralisation reaction, heat is always produced or evolved.
• The evolved heat raises the temperature of the reaction mixture. 

Explanation:-

Acid:

• The substances which have a sour taste are called acids.
• They turn blue litmus red.
• They easily give away H+ ions.
• Examples - HCl, H2SO4.

Base:

• The substances which have a bitter taste are called bases.
• They turn red litmus blue.
• They easily give away 0H- ions.
• Examples - NH4OH, NaOH.

Important Points

• Baking Soda:- It is a Bicarbonate of Sodium, which is alkaline by nature. It is commonly used as a leavening agent. When baking soda reacts with acid it releases CO2 and therefore it is the only cause of expansion and sponginess in Cakes, Dhoklas, etc. 
• Vinegar:- Vinegar is an aqueous solution of acetic acid in water. It is mainly used in food preservation.
• Lemon Juice:- Lime juice is acidic by nature. Lime juice contains citric acid and is used in the food industry, disinfectant, in medicines.
• Bleach:- The chemical compound which is used industrially to remove colour or stains from clothes or other substances. Bleaches are basic in nature.

 Additional Information

• Strong acid and a weak base result from a weakly acidic solution.
• A weak acid and a strong base result from a weakly basic solution. 
• The chemical species which can donate pair of electrons is said to be Lewis acid. Examples, H3O+, H+.
• The chemical species which can accept pair of electrons is said to be Lewis base. Example, OH-.

Key Points

• Tooth enamel begins to demineralize when the pH of the mouth drops below 5.5. This is known as the "critical pH" for enamel.
• At a pH lower than 5.5, the acidic environment allows bacteria like Streptococcus mutans and Lactobacillus to thrive, leading to tooth decay.
• The acid is primarily produced by bacteria as they metabolize sugars and carbohydrates present in food.
• Maintaining a pH level above 5.5 in the mouth is important to prevent enamel erosion and subsequent cavity formation.

Additional Information

• pH Scale:
  • The pH scale ranges from 0 to 14, where 0 is highly acidic, 7 is neutral, and 14 is highly alkaline.
  • The normal pH of saliva in a healthy mouth ranges between 6.5 to 7.5, which is slightly acidic to neutral.
• Tooth Enamel:
  • Tooth enamel is the hard, protective outer layer of the teeth. It is primarily composed of hydroxyapatite, a crystalline calcium phosphate.
  • Enamel is highly vulnerable to acidic environments, which can lead to its demineralization.
• Role of Bacteria:
  • Bacteria like Streptococcus mutans play a key role in tooth decay. They metabolize sugars and produce acids as byproducts.
  • The acids lower the pH of the mouth, creating an environment conducive to enamel erosion.
• Preventive Measures:
  • Regular brushing and flossing help remove food particles and plaque, reducing bacterial activity.
  • Using fluoride toothpaste strengthens enamel and helps resist acid attacks.
  • Avoiding sugary foods and drinks minimizes bacterial acid production.
  • Rinsing the mouth with water or mouthwash can help neutralize acid and restore pH balance.

The Correct answer is A salt and water are formed.

Key Points

• When an acid reacts with a metal oxide, a neutralization reaction takes place.
• In this reaction, the acid reacts with the basic metal oxide to form a salt and water.
• For example, when hydrochloric acid (HCl) reacts with magnesium oxide (MgO), the products are magnesium chloride (MgCl₂) and water (H₂O).
• The general form of this reaction can be written as: Acid + Metal Oxide → Salt + Water.
• This type of reaction is an important concept in chemistry and helps in understanding the nature of acids and bases.

 Additional Information

• A salt and hydrogen gas are formed
  • This option is incorrect because the formation of hydrogen gas typically occurs when an acid reacts with a metal, not a metal oxide.
  • For example, when hydrochloric acid (HCl) reacts with zinc (Zn), it produces zinc chloride (ZnCl₂) and hydrogen gas (H₂).

The correct answer is Methanoic acid.

Key Points

• Nettle is an herbaceous plant that grows in the wild.
• Nettle leaves have stinging hair, which causes painful stings when touched accidentally. 
• This is due to the methanoic acid secreted by them. 
• A traditional remedy is rubbing the area with the leaf of the dock plant, which often grows beside the nettle.

Additional Information

The correct answer is Less than 5.6.

Important Points

• Acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are discharged into the air.
• These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.
• Human activities are the main cause of acid rain.
• Over the past few decades, humans have released so many different chemicals into the air that they have changed the mix of gases in the atmosphere.
• Power plants release the majority of sulfur dioxide and much of the nitrogen oxides when they burn fossil fuels, such as coal, to produce electricity.
• Besides, the exhausts from cars, trucks, and buses release nitrogen oxides and sulphur dioxide into the air. These pollutants cause acid rain.

Key Points

• pH: Potential of Hydrogen
• pH is a measure of how acidic/basic water is.
• The range goes from 0 to 14, with 7 being neutral. pHs of less than 7 symbolize acidity, whereas a pH of greater than 7 indicates a base.
• The concept of pH value is introduced in 1909 by Søren Sørensen as a suitable way of expressing acidity—the negative logarithm of hydrogen ion concentration.

The correct answer is 7.35 - 7.45.

Key Points

• The pH range of a human body is 7.35 - 7.45.
• pH means the potential of Hydrogen.
• The pH scale is the scale used to express the acidity or alkalinity of a substance based on the concentration of hydrogen ions in its solution.
• pH scale was discovered by Soren Sorensen.
• The range of pH scale 0 to 14.
  • If pH < 7 then solution is acidic.
  • If pH > 7 then solution is basic.
  • If pH = 7 then solution is neutral
• The strength of acids and bases depends on the number of H+ ions and OH- ions produced, respectively.
• When the pH of rainwater is less than 5.6, it is called acid rain.
• The pH value of the Milk of Magnesia is 10.5.

The correct answer is Sulphurous acid.

Explanation:

When sulphur dioxide is dissolved in water it forms Sulphurous acid. The chemical formula of sulphur dioxide is SO₂.
The chemical equation is shown below. 

• SO₂ +H₂O ⟶ H₂SO₃
• Metallic oxides are formed when metals react with oxygen. Because they react with water to form bases, these metallic oxides are basic in nature. 
• Non-metals, on the other hand, react with oxygen to form non-metallic oxides, which differ from metallic oxides in that they are acidic. Non-metallic oxides also form acids when they react with water.
• Sulphur is a non-metallic element, and sulphur dioxide (SO₂) is acidic. As a result, it reacts with water to produce sulphurous acid (H₂SO₃)
• Properties of Sulphurous acid:
  • Sulphurous acid is a colourless liquid.
  • Sulphurous acid is a good reducing agent.
  • It is used as a mild bleaching agent for applications.
  • Sulphurous acid is unstable and has never been isolated in it its pure states.

Additional Information

• Sulphur Trioxide
  •  It reacts violently with water to form sulfuric acid with the release of heat.
• Sulphur Pentaoxide
  • No direct reaction.
• Sulphuric Acid
  • Water is less dense than sulfuric acid and will tend to float above the acid.
  • The reaction is best thought of as forming hydronium ions.

Mistake Points

•  Sulfur dioxide dissolves in water to give solutions that contain sulfurous acid H₂SO₃
• 2 SO₂ (aq) + 2 H₂O (l) + O₂ (g) → 2 H₂SO₄(aq)  formation of the sulphuric acid from the sulphur dioxide.

The correct answer is Orange.

Explanation:

• The fruits containing citric acid are termed as citrus fruits. eg: lemon, orange, grapefruit, etc.
• These are sour in taste and are a good source of Vitamin C, thus help in preventing the disease caused by the deficiency of Vitamin C, i.e., Scurvy.
• Grapes contain a lesser amount of citric acid than lime.
• Banana is a rich source of fiber, potassium, and Vitamin B6.
• Mango is a food source of fiber and Vitamin A and C. 

Few naturally occurring acids are -

• Antacid:
  • Antacids are medicines that counteract (neutralize) the acid in your stomach to relieve indigestion and heartburn.
  • Antacids may help if you have: 
    • Indigestion
    • Heartburn or acid reflux – also known as gastro-oesophageal reflux disease (GORD)
    • Stomach ulcer
    • Gastritis (inflammation of the stomach lining) 

Additional Information

• Antibiotic: 
  • These are medications that destroy or slow down the growth of bacteria. 
  • Antibiotics are used to prevent and treat bacterial infections.
• Analgesic:
  • Analgesics, also called painkillers, are medications that relieve different types of pain from headaches to injuries to arthritis.
  • Anti-inflammatory analgesics reduce inflammation, and opioid analgesics change the way the brain perceives pain. 
• Antiseptic:
  • An antiseptic is a substance that stops or slows down the growth of microorganisms.
  • They are frequently used in hospitals and other medical settings to reduce the risk of infection during surgery and other procedures.
• Milk of magnesia: Magnesium hydroxide is found in Milk of magnesia. It is used as an antacid. To reduce the excess of stomach acidity

The correct answer is Spinach.

Key Points

Concept:

• Acids
  • Acids are substances that taste sour. 
  • It turns blue litmus paper red. 
  • Acids are naturally present in citrus fruits like oranges, grapes, etc. 
  • It is also present in the ant's sting which causes irritation. 
  • Some naturally occurring acids and their source

Conclusion:

Oxalic acid is found in spinach. So, the correct option is spinach.

Additional Information

• Bases neutralizes acid. 
• They are bitter in taste, have a soapy feel, and turn red litmus blue. 

• The correct answer is option 4, i.e., Decreases 1000 times.
• When its pH changes to 6, then H+ ion concentration, decreases 1000 times.
• pH tells the concentration of hydrogen ions, lower the pH, higher is the hydrogen ion concentration.
• Acids have pH ranging from 1-6, pH 7 denotes neutral solution, and pH in the range of 8-14 denotes bases.
• The formula for calculating pH is: pH = - log [H +]
  • pH of 3 = 10 -3 H + 
  • pH of 6 = 10 -6 H +
• From the above values, we can clearly see that H + ion concentration decreases by 1000 times.

The correct answer is Nitric acid.

Key Points

• Nitric acid:
  • ​Nitric acid (HNO₃), is a highly corrosive and toxic strong mineral acid that is normally colorless but tends to acquire a yellow cast to the accumulation of oxides of nitrogen if long–stored.
• Applications:
  • Some precious metals such as gold and platinum do not react with nitric acid  hence it is used for cleaning purpose of these metals.
  • ​Nitric acid is used in the production of ammonium nitrate for fertilizers, making plastics, and in the manufacture of dyes.
  • Nitric acid is commonly used in science laboratories at schools for experimenting when specifically testing for chloride. 
  • Nitric acid has been used in various forms as the oxidizer in liquid–fueled rockets.

The correct answer is all of these.

• Acid
  • It reacts with active metals to yield hydrogen gas. and reacts with bases to produce a salt compound and water.
  • It tastes sour and changes blue litmus into red and phenolphthalein turns colorless in presence of acid.
  • Aqueous solutions of acids are electrolytes which means that they conduct an electrical current.
  • It capable of donating a proton and accepting an electron pair.
  • In water, it releases a proton (H⁺) into the solution.
  • The strong acids are hydrochloric acid, nitric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, perchloric acid, and chloric acid.

Additional Information

• Base
  • It has a bitter taste and changes red litmus into blue and phenolphthalein turns pink in the presence of a base.
  • It reacts with acids to produce a salt and water.