Recent questions in Chemistry

15.0 g of unknown molecular material was dissolved in 450 g of water. The resulting solution was found freezes at $−0.34^{\large\circ}$C. What is the molar mass of this material? ($K_f$ for water = $1.86 \;K\; kg \;mol^{−1}$)

asked Nov 16, 2016 by meena.p

1 answer

State a reason for each of the following solutions : (i) $CO^{2+}$ is easily oxidized to $CO^{3+}$ in the presence of a strong ligand (ii) $CO$ is a stronger complexing regent than $NH_3$ (iii) The molecular shape of $Ni(CO)_4$ is not the same as that of $[Ni(CN)_4]^{2-}$

asked Nov 16, 2016 by meena.p

1 answer

What is observed when : (i) A beam of light is passed through a colloidal solution ? (ii) Electric current is passed through a colloidal solution ?

asked Nov 16, 2016 by meena.p

1 answer

Give reasons— (a) Interhalogen compounds are more reactive than halogens (b) $PCl_5$ is known but $NCl_5$ is not known. (c) Amongst all noble gases, only xenon is known to form compounds with oxygen and fluorine.

asked Nov 16, 2016 by meena.p

1 answer

An aromatic compound $(A)$ on treatment with ammonia followed by heating forms compound $(B)$, which on heating with $Br_2$ and $KOH$ forms a compound $(C)$ having molecular formula $C_6H_7N$. Give the structures of $A, B$ and $C$ and write the reactions involved.

asked Nov 16, 2016 by meena.p

1 answer

Give one example for each of the following :(a) An artificial sweetener whose use is limited to cold drinks.(b) A non-ionic detergent.(c) A pain reliever used for relief from severe pains like post-operative pain or pain due to terminal cancer.

asked Nov 16, 2016 by meena.p

1 answer

(a) Give an example of a synthetic rubber and mention its main advantage. (b) Write the structures of the monomers of Dacron. (c) Arrange the following polymers in the increasing order of tensile strength. Nylon-6, Buna-S, Polythene.

asked Nov 16, 2016 by meena.p

1 answer

a)Give reasons for the following : (i) Glucose does not give 2,4-DNP test and Schiff’s test (ii) Amino acids have high melting points and are soluble in water. (b) What is meant by the secondary structure of proteins?

asked Nov 16, 2016 by meena.p

1 answer

In a hydrolysis reaction, $5\;g$ ethyl acetate is hydrolysed in presence of dilute HCl in $300\; minutes$. If the reaction is of first order and the initial concentration of ethyl acetate is $22\;g/L$, calculate the rate constant of the reaction.

asked Nov 16, 2016 by meena.p

1 answer

Draw the structure of the following $a)H_2S_2O_8 \\ b)X_eO_3 \\ c) HOClO_2 $

asked Nov 15, 2016 by meena.p

1 answer

(i) Why Grignard reagents should be prepared under anhydrous conditions. (ii) Why $C_6H_5CHClCH_3$ is hydrolysed more easily with $KOH$ than $C_6H_5CH_2Cl$

asked Nov 15, 2016 by meena.p

1 answer

Complete the following reactions : (i) $P_4 +8SOCl_2 \to \\ (ii)\;I^{-}+O_3+H_2O \to $

asked Nov 15, 2016 by meena.p

2 answers

a) What is the role of depressent in froth flotation process ? b) Out of C and CO, which is a better reducing agent for FeO? (i) In the lower part of blast furnace (Higher temperature ) (ii) In the upper part of blast furnace (lower temperature )

asked Nov 15, 2016 by meena.p

1 answer

Consider the decomposition of hydrogen peroxide in alkaline medium which is catalyzed by iodide cons . $2H_2O_2 \qquad \underrightarrow{-OH} \qquad 2H_2O+O_3$ This reaction takes place in two steps as given below Step I:$H_2O_2+I^{-} \to H_2O+I_0^{-}$ (slow) Step II:$H_2O_2+IO^{-} \to H_2O+I^{-}+O_2$ (fast) a) Write the rate law expression and determine the order of reaction w.r.t $H_2O_2$ b) What is the molecularity of each individual step ?

asked Nov 15, 2016 by meena.p

1 answer

Gold (atomic mass $=197\;v$ atomic radius $=0.144\;nm$) crystallizers in a face centered unit cell . Determined the density of gold $[N_A=6.022 \times 10^{23}mol^{-1}]$

asked Nov 14, 2016 by meena.p

1 answer

Write two important uses of formalin .

asked Nov 14, 2016 by meena.p

1 answer

What are the ultimate products of digestion of Proteins ?

asked Nov 14, 2016 by meena.p

1 answer

Why do amines act as nucleophiles ?

asked Nov 14, 2016 by meena.p

1 answer

Why is ferric chloride preferred over potassium chloride in case of a cut leading to bleeding?

asked Nov 14, 2016 by meena.p

1 answer

A and B liquids on mixing produce a warm solution . Which type of deviation from Raoult's law is there ?

asked Nov 14, 2016 by meena.p

1 answer

What happens when (i) Chorine gas is passed through a hot concentrated solution of $NaOH$? (ii) Sulphur dioxide gas is passed gas is passed through an aqueous solution of $Fe(III) $ salt ?

asked Nov 14, 2016 by meena.p

1 answer

Answer the following : (i) Haloalkanes easily dissolve in organic solvent why ? (ii) What is known as a racemic mixture ? Give an example

asked Nov 14, 2016 by meena.p

1 answer

Between Sodium hydrogen carbonate and magnesium hydroxide which is a better antacid and why ?

asked Nov 14, 2016 by meena.p

1 answer

Write about the following on protein synthesis. (a) Name the location where protein synthesis occurs . (b) How do 64 codons code for only 20 amino acids (c) Which of the two bases of the codon are more important for coding ?

asked Nov 14, 2016 by meena.p

1 answer

Write the following conversions : $(i) nitrobenzene \to acetanilide \\ (ii) acetanilide \to p-nitroanilne$

asked Nov 11, 2016 by meena.p

1 answer

Account for the following : Sodium bisulphites is used for the purification of aldehydes and ketones .

asked Nov 11, 2016 by meena.p

1 answer

(a) Give the equation of reaction for the preparation of phenol from cumene. (b) Write the chemical reaction for the preparation of phenol from chloro benzene

asked Nov 11, 2016 by meena.p

1 answer

Explain giving a suitable reason for each of the following : a)Transition metal and their compounds are generally found to be good catalysts. b) Transition metal and their compounds generally exhibit a para-magnetic behaviour .

asked Nov 11, 2016 by meena.p

1 answer

Explain why inspite of nearly the same electronegativity , oxygen forms hydrogen bonding while chloride does not

asked Nov 11, 2016 by meena.p

1 answer

State the reason in each of the following cases: (i) Soaps do not work well in hard water (ii) Synthetic detergents are better than soaps .

asked Nov 10, 2016 by meena.p

1 answer

Distinguish between rate expression and rate constant of a reaction

asked Nov 10, 2016 by meena.p

1 answer

Calculate the amount of KCl which must be added to $1\;kg$ of water so that the freezing point is depressed by $2\;k$? ($k_f$ for water = $1.86 \;K \;mol^{-1}$)

asked Nov 10, 2016 by meena.p

1 answer

Give the preparation and uses of PVC

asked Nov 10, 2016 by meena.p

1 answer

a)Give chemical tests to distinguish between compounds in each of the following pairs: i) Benzaldehyde and Acetone ii)Phenol and Ethanol b)Give reasons for the following: i)Although –$NH_2$ group is an ortho and para directing group, nitration of aniline gives along with ortho and para as well as meta derivative also, why? ii)Conc.HI is preferable used in the cleavage of ether linkage. Explain. iii)Out of $PCl_5$ and $SOCl_2$ which one is a better reagent for the conversion of alcohol to alkyl chloride and why?

asked Nov 10, 2016 by meena.p

1 answer

Account for the following: i)Fluorine does no show variable oxidation states while other members of the halogen family exhibit variable oxidation states. ii)Iodine is more soluble in $KI$ solution than in water. iii)Why do boiling points of noble gases increases down the group? iv)Why ammonia is a good complexing agent? v)Nitric oxide(NO) is a colourless gas becomes brown when released in air.

asked Nov 10, 2016 by meena.p

1 answer

a)i)The resistance of a conductivity cell containing $0.001\;M\; KCl$ solution at $298\;K$ is $1500 \Omega$. What is the cell constant, if the conductivity of $0.001\;M\; KCl$ solution at $298\;K$ is $0.146 \times 10^{-3}\;S\;cm^{-1}$? ii)Explain with one example each the terms weak and strong electolytes iii)The standard reduction potential values of three metallic cations $X,Y, Z$ are $+0.52, − 3.03, − 1.18 V$ respectively. What will be the order of reducing power of the corresponding metals? b) Distinguish between rate expression and rate constant of a reaction

asked Nov 10, 2016 by meena.p

1 answer

(a) Bring out the following conversions:. (i) 4-nitrotoluene to 2-bromobenzoic acid. (ii) Ethylcyanide to 1- phenyl propanone. (b) Give a reason for the following : (i) Chloroacetic acid is more acidic than acetic acid. (ii) Carboxylic acids have higher boiling point than alcohols. (iii) 4-nitrobenzoic acid is more acidic than 4-methoxy benzoic acid.

asked Nov 10, 2016 by meena.p

1 answer

(a) Compare non transition and transition elements on the basis of their (i) Variability of oxidation states (ii) stability of oxidation states. (b) Give chemical reactions for the following observations: (i) Potassium permanganate is a good oxidising agent in basic medium. (ii) Inter convertibility of chromate ion and dichromate ion in aqueous solution depends Upon pH of the solution. (iii) Potassium permanganate is thermally unstable at $513\;K$.

asked Nov 10, 2016 by meena.p

1 answer

(I)(a) Calculate the boiling point of a solution containing $0.61\;g$ of benzoic acid in $5\; g$ of $CS_2$ .Assuming $84\%$ dimerisation of acid. The boiling point and $K_b$ of $CS_2$ are $46.2^{\circ}0C$ and $2.3\; K\; Kg \;mol^{-1}$ respectively. (b) State Raoult's law for the solution containing non-volatile solute. Give its mathematical expression also. (II) A solution of $KMnO_4$ on reducing yields either a colourless solution or a brown precipitate or a green solution depending on $PH$ of the solution . What different stages of the reduction do these represent and how are they carried out ?

asked Nov 10, 2016 by meena.p

1 answer

How would you account for the following : (i) The following order of increase in strength of acids $PH_3 < H_2S < HCl $ (ii) The oxidizing power of oxo-acids of chlorine follows the order . $HClO_4 < HClO_3 < HClO_2 < HClO$

asked Nov 9, 2016 by meena.p

1 answer

Out of C and CO, Which is better reducing agent at $673\;k$

asked Nov 9, 2016 by meena.p

1 answer

Why is an increase in temperature observed on mixing chloroform with acetone ?

asked Nov 9, 2016 by meena.p

1 answer

Ionic solid conduct in the molten state but not in the solid state . Explain

asked Nov 9, 2016 by meena.p

1 answer

(a) Write a suitable chemical equation to complete each of the following transformations: (i) Butan-1-ol to butanoic acid . ( ii) 4 -Methylacetophenone to benzene -1,4-dicarboxylic acid (b) Suggest a reagent for conservation of ethanol to ethanoic acid

asked Nov 9, 2016 by meena.p

1 answer

(a)Define the following terms : (i) Mole fraction (ii) Ideal solution (b) For the reaction $A \to B$ ,the rate of reaction becomes twenty seven times when the concentration of A is increased three times . What is the order of the reaction ?

asked Nov 9, 2016 by meena.p

1 answer

(a)Draw the molecular structure of the following compounds : $(i)N_2O_5 (ii) X_eOF_4$ (b) Why do the d-block elements exhibits a large number of oxidation states than f - block elements

asked Nov 8, 2016 by meena.p

1 answer

Pickles have a long self - life and do not get spoiled for month . why ?

asked Nov 8, 2016 by meena.p

1 answer

a)What are polysaccharides ? Give one example b)Give the preparation and uses of PVC

asked Nov 8, 2016 by meena.p

1 answer

Name the alkyl halide and sodium alkaloid used to synthesize tert - butyl ether

asked Nov 8, 2016 by meena.p

1 answer

Arrange following complex ions in increasing order of crystal field splitting energy $(\Delta _0)$: $[Cr(Cl)_6]^{3-},[Cr(CN)_6]^3,[Cr(NH_3)_6]^{3+}$

asked Nov 8, 2016 by meena.p

1 answer

Ask Questions, Get Answers