What is the action of litmus on ethanol ?
- A.Litmus is neutral towards ethanol
- B.Ethanol turns blue litmus to red; confirming acidic nature of ethanol
- C.Ethanol turns red litmus to blue; confirming basic nature of ethanol
- D.Ethanol decolorizes litmus through bleaching action
Correct answer
Explanation
The correct answer is A, Litmus is neutral towards ethanol. Ethanol does not change the colour of either red or blue litmus, because it is neutral.
Ethanol, C₂H₅OH, is an alcohol. Its –OH group is bonded to carbon by a covalent bond and does not release hydroxide ions in water, so it is not a base; nor does it give off hydrogen ions the way an acid does. That is why the litmus test separates ethanol from ethanoic acid, which turns blue litmus red. Ethanol does react with sodium metal to give hydrogen gas, which shows it is very weakly acidic, but far too weakly to affect litmus.
B is wrong because turning blue litmus red is a test for ethanoic acid, not ethanol.
C is wrong because ethanol gives no hydroxide ions and so cannot turn red litmus blue.
D is wrong because ethanol is not a bleaching agent; chlorine water and sulphur dioxide bleach litmus.
Exam tip: ethanol is neutral to litmus; ethanoic acid turns blue litmus red and fizzes with sodium hydrogencarbonate.
Practice Questions
View allConsider the following pairs : (Commonly used / consumed materials : Unwanted or controversial chemicals likely to be found in them) 1. Lipstick : Lead 2. Soft drinks : Brominated vegetable oils 3. Chinese fast food : Monosodium glutamate Which of the pairs given above is/are correctly matched ?
- A.1 only
- B.2 and 3 only
- C.1 and 3 only
- D.1, 2 and 3
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Each product has been linked to the chemical paired with it. Lead has been found as a trace contaminant in many lipsticks, coming from colour pigments; since lipstick is swallowed in small amounts, regular use raises concern because lead is a toxic heavy metal that harms the nervous system.
Read the full explanation →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.
Show answer
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
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.
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