Recent questions in Chemistry

Which of the following polymers soften on heating and harden on cooling? What are the polymers with this property collectively called? What are the structural similarities between such polymers?

asked Nov 28, 2016 by meena.p

1 answer

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

asked Nov 28, 2016 by meena.p

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State reasons for the following : (i) $pKb$ value for aniline is more than that for methylamine. (ii) Ethylamine is soluble in water whereas aniline is not soluble in water. (iii) Primary amines have higher boiling points than tertiary amines.

asked Nov 28, 2016 by meena.p

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Draw the structure of : (i) 3- methyl butanal (ii) 4- chloropentan-2-one (iii) 3-oxopentanal

asked Nov 25, 2016 by meena.p

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Give names of the reagents to bring about the following transformations: (i) Hexan-1-ol to hexanal (ii) Cyclohexanol to cyclohexanone (iii) P-Fluorotoluene to p-Fluorobenzaldehyde (iv) Ethanenitrile to ethanal (v) Allyl alcohol to propenal

asked Nov 25, 2016 by meena.p

1 answer

How would you account for the following (i) Aldehydes are more reactive than ketones towards nucleophiles (ii) The boiling points of aldehydes and ketones are lower than of the corresponding acids (iii) The aldehydes and ketones undergo a number of addition reactions.

asked Nov 25, 2016 by meena.p

1 answer

$Fe^{3+} \longrightarrow (A) \quad \longrightarrow \quad (B)$ What are (A) and (B) ? Give IUPAC name of (A) . Find the Spin only magnetic moment of $(B)$

asked Nov 25, 2016 by meena.p

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(i) Are all the five bonds in $PCl_5$ molecules equivalent ? justify your answer. (ii) What happens when $PCl_5$ is heated ?

asked Nov 25, 2016 by meena.p

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(a) Why refractory metals are used in the construction of furnaces ? (b) What is pyrometallurgy ?

asked Nov 25, 2016 by meena.p

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Explain how the phenomenon of absorption finds application in each of the following process : (i) Production of vaccum (ii) Heterogeneous catalysis

asked Nov 25, 2016 by meena.p

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Iron and nickel are used to make electro chemical cell by using a salt bridge to join a half cell containing $1\;M\;Fe^{2+}(aq)$ in which a strip of irons has been immersed to a second half cell which contain $1\;M\;Ni^{2+}(aq)$ in which a strip of Ni has been immersed ? A voltmeter is connected between the two metal strips : $E^{0} _{Fe^{2+}/Fe} =-0.44 V; \qquad E^{0} _{Ni^{2+}/Ni} =-0.25 V $ a) Write the name of the cathode and anode . b) Write the half reaction involved ? c) What would be the effect on the voltmeter reading if $Fe^{2+}$ concentration were increased ?

asked Nov 24, 2016 by meena.p

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When fruits and vegetables that have dried are placed in water , they slowly swell and return to the original form . Explain why ? Would a temperature increase accelerate the process explain .

asked Nov 24, 2016 by meena.p

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Which of the following does not react with oxygen directly ? why ? $Zn,Ti,Pt,Fe$

asked Nov 24, 2016 by meena.p

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Which of the following pair will have greater conduction and why ? (a) Copper wire at $25^{\circ}C$ and copper wire at $50^{\circ}C$. (b) $0.1\; M$ acetic acid solution or $1\;M$ acetic acid solution?

asked Nov 24, 2016 by meena.p

1 answer

Which colligative properly is preferred for the molar mass determination of macro molecules ? why ?

asked Nov 24, 2016 by meena.p

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Analysis shows that nickel oxide has the formula $Ni0_{98}O_{1.00}$. What fractions of nickel exist as $Ni^{2+}$ and $Ni_{3+}$ ions?

asked Nov 23, 2016 by meena.p

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Give reason (a) window glass of old building look milky. (b) window glass of old building is thick at bottom (c) $Cacl_2$ will introduced schotlky defect if added to $Agcl$ crystal

asked Nov 23, 2016 by meena.p

1 answer

How is the basic strength of aromatic amines affected by the presence of an electron releasing group on the benzene ring ?

asked Nov 23, 2016 by meena.p

1 answer

What is the value of X in the complex $H_xCo(Co)_4$ on the basis of $EA N$ rule . $(At . No.CO=27)$

asked Nov 23, 2016 by meena.p

1 answer

Why the bond angles is in the following order ? $NH_3=106.5^{\circ} ,\quad\;PH_3=93.5 ^{\circ}, \quad , ASH_3=91.5^{\circ}, \quad ,SbH_3=91.3^{\circ}$

asked Nov 23, 2016 by meena.p

1 answer

Why ICl bonds are weaker than $Cl_2$

asked Nov 23, 2016 by meena.p

1 answer

Dialysis is a method of purification of sols, But prolonged dialysis of the sol makes it unstable . Why ?

asked Nov 23, 2016 by meena.p

1 answer

An aromatic compound 'A' on treatment with $CHCl_3/KOH$ gives two compounds 'B' and 'C'. Both B and C give the same product 'D' when distilled with zinc dust. oxidation of D gives E having molecular formula $C_7H_6O_2$. The sodium salt of E on heating with sodalime gives F which may also be obtained by distilling A with Zinc dust . Identify A to F

asked Nov 23, 2016 by meena.p

1 answer

Assign reasons for the following: (i) The enthalpies of atomisation of transition elements are high. (ii) The transition metals and many of their compounds act as good catalysts. (iii) From element to element the actinoid contraction is greater than the lanthanoid contraction. (iv) The $E^{\circ}$ value for the $Mn ^{3+} / Mn ^{2+}$ couple is much more positive than that of $Cr^{3+} / Cr^{2+}.$ (v) Scandium $(z=21)$ does not exhibit variable oxidation states and yet it is regarded as a transition element

asked Nov 22, 2016 by meena.p

1 answer

Decomposition of phosphine $(PH_3)$ at $120^{\circ}C$ proceeds according to the equation: $4PH_3(g) \to P_4(g) + 6H_2(g)$ It is found that this reaction follows the following rate equation: Rate $= k[PH_3]$ The half-life of $PH_3$ is $37.9\;s$ at $120^{\circ}C.$ (i) How much time will be required for $\large\frac{3}{4}$ of $PH_3$ to decompose? (ii) What fraction of the original amount of $PH_3$ will remain undecomposed after 1 minute?

asked Nov 22, 2016 by meena.p

1 answer

On visit to your native village, you find that lot of smoke, dust and some other gases are coming out of the chimney of a recently set up factory near the village which is the cause of many respiratory problems for the people living there. Answer the following questions (i) As a chemistry student, what method you will suggest the factory owner to manage dust and smoke? (ii) What is the basic principle involved in your suggestion? (iii) What values are associated with your advice?

asked Nov 22, 2016 by meena.p

1 answer

Explain elastomeric polymers and fibres

asked Nov 22, 2016 by meena.p

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Glucose or sucrose are soluble in water but cyclohexane or benzene are insoluble in water. Explain.

asked Nov 22, 2016 by meena.p

1 answer

Arrange the following (i) In decreasing order of basic strength in gas phase : $C_2H_5NH_2, (C_2H_5)_2NH, (C_2H_5)_3 N$ and $NH_3$ (ii) In increasing order of boiling point : $C_2H_5OH, (CH_3)_2NH,C_2H_5NH_2$

asked Nov 22, 2016 by meena.p

1 answer

An organic compound $(A)\; \{C_8H_{16}O_2\}$ was hydrolysed with dilute sulphuric acid to give a carboxylic acid $(B)$ and an alcohol $(C)$. Oxidation of $(C)$ with chromic acid produced $(B)$.$(C)$ on dehydration gives but‐1‐ene .Identity $A,B,C$

asked Nov 22, 2016 by meena.p

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(i) Why pH of reaction should be carefully controlled while preparing ammonia derivatives of carbonyl compound? (ii) Why formic acid is stronger acid than acetic acid

asked Nov 22, 2016 by meena.p

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How would you account for the following $NF_3$ is an exothermic compounds but $NCl_3$ is not.

asked Nov 22, 2016 by meena.p

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Why is the silver plating of copper $k[Ag(CN)_2]$is used instead of $AgNO_3$ ?

asked Nov 22, 2016 by meena.p

1 answer

Complete the following chemical equations : (i) $P_4+SO_2 Cl_2 \to \\ (ii)Fe^{3+}+SO_2+H_2O \to \\ (iii) X_eF_6+H_2 O \to $

asked Nov 22, 2016 by meena.p

1 answer

Describe how the following changes are brought about : (i) Pig irons into steel (ii) Zinc oxide into metallic zinc

asked Nov 22, 2016 by meena.p

1 answer

$SnO_2$ forms a positively charged colloidal Sol in the basic medium why ?

asked Nov 22, 2016 by meena.p

1 answer

The following curve is obtained when molar conductivity $(\lambda_m)$ is plotted against the square root of concentration for 2 electrolytes A and B (a) What can you say about the nature of the two electrolyte $A\; \&\;B$ (b) How do you account for the increase in molar conductivity $\lambda_m$ for the electrolyte A and B on dilution

asked Nov 21, 2016 by meena.p

1 answer

$18\;g$ of glucose , $C_6H_{12}$ is dissolved in $1\;kg$ of water in a sauce pan. At what temperature will water boil at $1.013$ bar ? $K_b$ for water is $0.52\;k\;kg\;mol^{-1}$

asked Nov 21, 2016 by meena.p

1 answer

Give reasons for the following : (i) Nitric oxide become brown when released in air . (ii) Ammonia acts as a ligand.

asked Nov 21, 2016 by meena.p

1 answer

How is ferromagnetism different from paramagnetism

asked Nov 21, 2016 by meena.p

1 answer

The conductivity of $0.20\;M$ solution of KCl at $298\;K$ is $0.0248 \;Scm^{-1}$ Calculate its molar conductivity

asked Nov 21, 2016 by meena.p

1 answer

Why does the electrical conductivity of semiconductor increase in temperature ?

asked Nov 21, 2016 by meena.p

1 answer

How does sprinkling of salt help in clearing the snow covered roads in hilly areas? Explain the phenomenon involved in the process.

asked Nov 21, 2016 by meena.p

1 answer

Why is aniline soluble in aqueous HCl?

asked Nov 17, 2016 by meena.p

1 answer

Why $BH^{-} _ {4}$ and $NH_4^{+} $ are isolobal.

asked Nov 17, 2016 by meena.p

1 answer

Calculate the overall complex dissociation equilibrium constant for the $Cu(NH_3) _4^{2+}$ ion given that $B_4$ for this complex is $2:1 \times 10^{13}$

asked Nov 17, 2016 by meena.p

1 answer

In the preparation of $H_2SO_4$ by contact process , why is $ SO_3$ hot absorbed directly in water to form $H_2SO_4$?

asked Nov 17, 2016 by meena.p

1 answer

Write two difference between sols and emulsions.

asked Nov 17, 2016 by meena.p

1 answer

Explain : (i) The molecules $NH_3$ and $NF_3$ have dipole moments which are of opposite direction . (ii) Sulphur in vapour state exhibits paramagnetism

asked Nov 17, 2016 by meena.p

1 answer

Explain the following terms giving one example of each type (i) Antacids (ii) Disinfectants

asked Nov 17, 2016 by meena.p

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