What are the main constituents of biogas?
- A.Methane and sulphur dioxide
- B.Methane and carbon dioxide
- C.Methane, hydrogen and nitric oxide
- D.Methane and nitric oxide
Correct answer
Explanation
The correct answer is B, Methane and carbon dioxide. Biogas is mainly methane and carbon dioxide.
Biogas is produced when bacteria break down animal dung, crop waste and kitchen waste in the absence of oxygen, a process called anaerobic digestion. It usually contains about 50 to 75 per cent methane and 25 to 45 per cent carbon dioxide, with small amounts of hydrogen sulphide, hydrogen and water vapour. The methane makes it a clean fuel for cooking and lighting in villages, and the slurry left in the plant is a good manure. In India it is often called gobar gas because cow dung is the most common raw material.
A is wrong because sulphur dioxide is not a main part of biogas; only traces of hydrogen sulphide are present. C is wrong because hydrogen and nitric oxide are not its main constituents. D is wrong because nitric oxide is not produced in biogas digestion; the second main gas is carbon dioxide.
Exam tip: Biogas = methane (50-75%) + carbon dioxide; made by anaerobic digestion; also called gobar gas.
Practice Questions
View allWhich one of the following is not true for anodizing process?
- A.It makes aluminium corrosion resistant.
- B.Metals like aluminium, titanium and magnesium can be anodized.
- C.Clean aluminium article is the anode and oxygen gas is evolved at the cathode.
- D.It is used in aircraft industry.
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In anodizing the clean aluminium article is indeed the anode, but oxygen is released at the anode, not at the cathode; hydrogen is released at the cathode.
Read the full explanation →Which one of the following statements is not correct?
- A.The response of the ear to sound of increasing intensity is approximately logarithmic.
- B.The sensitivity of the human ear does not vary with the frequency of the sound.
- C.When two or more waves traverse the same medium, the displacement of any element of the medium is the algebraic sum of the displacements due to each wave.
- D.Longitudinal waves can travel in all media—solids, liquids and gases.
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The statement that the sensitivity of the human ear does not vary with frequency is false, because the ear is far more sensitive to some frequencies than to others.
Read the full explanation →Kwashiorkor disease in children is caused by
- A.sufficient carbohydrates but less fats in diet
- B.sufficient carbohydrates and fats but deficient proteins in diet
- C.sufficient vitamins but deficient fats in diet
- D.sufficient fats but deficient vitamins in diet
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Kwashiorkor is a disease of protein deficiency in a child who still gets enough calories. It usually appears when a child is weaned from breast milk onto a starchy diet with little protein.
Read the full explanation →Which one of the following is the correct order of pH for the given substances?
- A.Coffee < Lemon juice < Milk of magnesia < Blood
- B.Milk of magnesia < Blood < Coffee < Lemon juice
- C.Lemon juice < Blood < Coffee < Milk of magnesia
- D.Lemon juice < Coffee < Blood < Milk of magnesia
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Arranged from most acidic to most basic, the four substances fall in exactly this order. Lemon juice, rich in citric acid, has a pH of about 2 to 2.5.
Read the full explanation →Which one of the following diseases may be caused by the deficiency of vitamin C?
- A.Rickets
- B.Rabies
- C.Hepatitis
- D.Scurvy
Show answer
Scurvy is caused by a lack of vitamin C, or ascorbic acid, which the body needs to make collagen, the protein that holds skin, gums and blood vessels together.
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