Recent questions tagged acids

Description : Explain why o-hydroxybenzaldehyde is a liquid at room temperature while p-hydroxybenzaldehyde is a high melting solid.

Last Answer : Due to interamolecular H-bonding ortho-hydroxy benzaldehyde exists as discrete molecule whereas due to intermolecular H-bonding, p-hydroxybenzaldehyde exists as associated molecules. To break these intermolecular ... a liquid at room temperature while p-hydroxy benzaldehyde is a high melting solid. 

Description : Arrange the following carboxyl compounds in increasing order of their reactivity in nucleophilic addition reactions. Explain with proper reasoning : Benzaldehyde. p-tolualdeyde, p-nitrobenzaldehyde, Acetophenone.

Last Answer : Ans. Acetophenone is a ketone while all others are aldehydes, therefore it is least reactive. In p-tolualdehyde, there is methyl group (CH3 ) at para position w.r.t. to the ... overall order of increasing reactivity : acetophenone < p-tolualdehyde < benzaldehyde < p-nitrobenzaldehyde. 

Description : Why does solubility decreases with increasing molecular mass in carboxylic acid ?

Last Answer : Ans. Because of increase in alkyl chain length which is hydrophobic in nature. 

Description : Why does methanal undergoes Cannizaro’s rxn ?

Last Answer : Ans. Because it does not possesses hydrogen atom. Only those aldehydes can undergo  Cannizaro reaction which do not possess hydrogen atoms.

Description : Why does methanal not give aldol condensation while ethanol gives ? 

Last Answer : Ans. This is because only those compounds which have hydrogen atoms can undergo  aldol reaction. Ethanol possesses -hydrogen and undergoes aldol condensation.   Methanal has no hydrogen atoms, hence does not undergo aldol condensation. 

Description : What are Hemiacetal and acetal ? 

Last Answer : Ans. Hemiacetal and acetals are formed by addition of alcohols on carboxyl compounds.  

Description : Would you expect benzaldehyde to be more reactive or less reactive in nucleophlic addition reaction than propanal ? Explain.

Last Answer : C-atom of carbonyl group of benzaldehyde is less electrophilic than C-atom of carbonyl group in propanal. Polarity of carbonyl group is in benzaldehyde reduced due to resonance making it less ... group in it is more than in benzaldehyde. This makes propanal more reactive than benzaldehyde. 

Description : Why pcc cannot oxidise methanol to methane and while KMnO4 can ?

Last Answer : This is because pcc is a mild oxidising agent and can oxide methanol to methanal only. While KMnO4 being strong oxidising agent oxidises it to methanoic acid. 

Description : Give the composition of Fehling A and Fehling B ?

Last Answer : Ans. Fehling A = aq. CuSO4 Fehling B = alkaline sodium potassium tartarate (Rochelle Salt)

Description : Why are aldehydes more reactive than ketones ? 

Last Answer : Ans. It is because of 2 reasons : The carboxyl compounds (both aldehydes & ketones) undergo nucleophilic addition reaction. (i) + I effect : The alkyl group in ketones due to their e- ... its reactivity. (ii) Steric hindrance : Due to steric hindrance in ketones, they are less reactive.

Description : Distinguish between : (i) Acetaldehyde and acetone (ii) Methanoic acid and Ethanoic acid.

Last Answer : (i) Acetaldehyde will give positive tests with Tollen’s reagent and Fehling Solns. whereas acetone will not give these test. (ii) Methanoic acid gives Tollen’s reagent test whereas ethanoic acid does not due to difference in their boiling points.

Description : Arrange the following compounds in increasing order of their acid strength. Benzoic acid, 4-Nitrobenzoic acid, 3, 4-dinitrobenzoic acid, 4-methoxy benzoic acid.

Last Answer : Since electron donating gps. decrease the acid strength therefore 4-methoxybenzoic acid is a weaker acid because methoxy sp. is E. D. G. than benzoic acid. Further since electron withdrawing gps. increase ... : 4-methoxybenzoic acid < benzoic acid < 4-nitrobenzoic acid < 3, 4, dinitrobenzoic acid.

Description : During preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst, water or the ester formed should be removed as soon as it is formed.

Last Answer : Ans. The formation of esters from a carboxylic acid and an alcohol in the presence of acid catalyst in a reversible reaction. To shift the equilibrium in the forward direction, the water or ester formed should be removed as fast as it is formed.

Description : Why HCOOH does not give HVZ (Hell Volhand Zelinsky) reaction but CH3COOH does ?

Last Answer : Ans. CH3 COOH contains hydrogens and hence give HVZ reaction but HCOOH does  not contain -hydrogen and hence does not give HVZ reaction. 

Description : What makes acetic acid a stronger acid than phenol ?

Last Answer : Ans. Greater resonance stabilization of acetate ion over phenoxide ion. 

Description : What type of aldehydes undergo Cannizaro reaction ?

Last Answer : Ans. Aromatic and aliphatic aldehydes which do not contain hydrogens. 

Description : Suggest a reason for the large difference in the boiling points of butanol and butanal, although they have same solubility in water.

Last Answer : The b. pt. of butanol is higher than that of butanal because butanol has strong intermolecular H-bonding while butanal has weak dipole-dipole interaction. However both of them form H-bonds with water and hence are soluble.

Description : Define indicator

Last Answer : A substance shows different colour in acidic and basic solutions. e.g. phenolphthalein, methyl orange, litmus, turmeric, China rose and red cabbage.

Description : How we can measure PH of a solution?

Last Answer : The PH can be measure with universal indicator or PH paper. A universal indicator paper has a mixture of several dyes coated on it. It shows different colours for each PH values.

Description : What is PH Scale?

Last Answer : A scale used to measures the acidic or basic or alkaline solution is known as PH scale.

Description : Write the use of ammonium Hydroxide

Last Answer : Ammonium hydroxide used in: I. To remove grease from window panes II. To remove ink spots from clothes III. As a regent in laboratory IV. For the treatment of bee’s string

Description : Write the use of calcium Hydroxide

Last Answer : Calcium hydroxide used in: I. In the manufacture of bleaching powder II. As a dressing material for acid burns III. In making lime sulphur sprays to be used as fungicide IV. As a water softener V. For neutralization acidity present in soil

Description : Write the use of Sodium Hydroxide

Last Answer : Sodium hydroxide used in: I. Soap, textile and plastic industries. II. Petroleum refining. III. Making rayon IV. In the manufacture of paper pulp and medicines.

Description : Write the use of Acetic acid

Last Answer : Acetic acid used in: I. In the preparation of pickles (ACHAAR) II. In the manufacture of synthetic fiber.

Description : Write the use of Sulphuric acid H2SO4

Last Answer : Sulphuric acid 24 used in: I. As a dehydrating agent II. In the manufacture of fertilizers like ammonium phosphate, calcium ammonium phosphate, calcium super phosphate etc. III. In the manufacture of ... IV. In petroleum refining, textile, paper and leather industries. V. In lead storage batteries.

Description : Write the use of Nitric Acid HNO3

Last Answer : I. In the manufacture of fertilizers like ammonium nitrate II. For the manufacture of explosives III. In the manufacture of dyes, plastics and artificial silk. IV. For etching designs on metals like copper brass and bronze.

Description : Write the use of HCl

Last Answer : I. For cleaning rust from the surface of metals. II. For purification of Common salt (NaCl). III. To make aqua regia (3HCl + HNO3) used to dissolve noble metals such as gold. IV. For making glucose from starch. V. For the proper digestion of food in our stomach.

Description : How litmus solution is prepared?

Last Answer : Litmus solution is prepared by dissolving red cabbage juice or turmeric powder.

Description : Which alkali is commonly used to open a drain?

Last Answer : Potassium carbonate strong alkaline solution is used to open a drain.

Description : Is soda water acidic or basic?

Last Answer : Soda water is acidic

Description : State the properties of Acids

Last Answer : I. All acids have sour taste II. All acids turn blue litmus solution and methyl orange solution Red. III. Strong acids are corrosive liquids. They burn skin and destroy fabrics and animal tissues. IV. ... of electricity. V. Acids react with reactive metals (Mg, Zn) to form salt and evolve hydrogen.

Description : The concentraction of hydrogen ion (H+ )is denoted by pH.How do you denote concentration of hydrogen ion(OH)?

Last Answer : Ans:The concentration of hydrogen ion (OH) is denoted by poH.

Description : If some solution has pH=5.5 then what will be its poH?

Last Answer : PH=5.5 PoH=? We know that PH+poH=14 5.5+poH=14 poH=14-5.5=8.5

Description : What is sum of pH &poH in any solution?

Last Answer : Ans: PH + poH = 14

Description : What is meant by term “pH”?

Last Answer : The –ve log of hydrogen ion concentration , present in a solution is called pH. PH= -log[H+ ]

Description : What is potash alum?

Last Answer : Ans:It is double salt obtained by dissolved equimolar quantities of potassium sulphate and aluminum sulphate in water .This is very useful salt and used for dying and other process.

Description : Why ammonia solution is used for the cure of honey bee sting, whereas vinegar is used for curing sting of wasp?

Last Answer : Ans: Honey bee sting is acidic so to neutralize its effect we use a basic ammonia solution. Whereas sting of wasp is alkaline so we use vinegar( weak acid) for cure.

Description : How degree of ionization effects the strength of an acid or base according to Arrhenius concept?

Last Answer : Ans: An acid or base which will ionize completely, having high degree of ionization, will give more H+ or –OH ions. And will be a strong acid or base.

Description : Why name acid was given to compounds ?

Last Answer : The word acid is derived from a Latin word Acidus that mean “sour”. This name was given because the acids discovered in beginning had sour taste.

Description : How are omega-3 fatty acids good for you?

Last Answer : After numerous scientific studies, it has been proven that polyunsaturated omega-3 fatty acids, which include eicosopentaenoic, docosahexaenoic, alpha-linolenic, are very beneficial for human health. They ... Taking only 2 g per day, you can insure against dementia, neuropathy and atherosclerosis.