Which 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.
Correct answer
Explanation
The correct answer is C. 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.
Anodizing is an electrolytic process, usually carried out in dilute sulphuric acid. The oxygen formed at the anode reacts with the aluminium surface and builds a thick, hard layer of aluminium oxide. This layer protects the metal from corrosion, resists wear and can absorb dyes, which is why anodized cookware and window frames come in many colours. The name itself comes from the article being made the anode.
A is true because the thicker oxide layer makes aluminium highly resistant to corrosion. B is true because aluminium, titanium and magnesium, and some other metals, all form stable oxide films and can be anodized. D is true because anodized aluminium alloys are widely used for aircraft parts, where light weight and corrosion resistance both matter.
Exam tip: anodizing means the article is the anode, oxygen forms at the anode and a protective oxide layer grows on it.
Practice Questions
View allWhich 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.
Show answer
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
Show answer
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
Show answer
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.
Read the full explanation →How many covalent bonds are present in a Chloropropane molecule having molecular formula, C₃H₇Cl?
- A.6
- B.8
- C.9
- D.10
Show answer
Chloropropane has two carbon–carbon bonds, seven carbon–hydrogen bonds and one carbon–chlorine bond, all single covalent bonds, making 10 in total.
Read the full explanation →