Chemistry Questions and Answers August 30, 2020

Write the reactions of Williamson synthesis of 2ethoxy3methylpentane starting from ethanol and 3 methylpentan2ol.

What is meant by hydroborationoxidation reaction Illustrate it with an example.

Give the equations of reactions for the preparation of phenol from cumene.

Write the mechanism of hydration of ethene to yield ethanol.

Show how will you synthesize (i) 1phenylethanol from a suitable alkene. (ii) cyclohexylmethanol using an alkyl halide by an S,2 reaction. (iii) pentan1ol using a suitable alkyl halide

Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.

Give equations of the following reactions (i) Oxidation of propan1ol with alkaline KMnO, solution. (ii) Bromine in CS with phenol. (iii) Dilute HNO, with phenol. (iv) Treating phenol with chloroform in presence of aqueous NaOH.

Write down the Arrhenius equation. Derive an expression for temperature variations. At a temperature of 600 K, the rate constant of a chemical reaction is 2.75108 M s. When the temperature is increased to 800K, the rate constant for the same reaction is 1.9510 7Ms. What is the activation energy of this reaction

How are the following conversions carried out (i) Propene Propan2ol (ii) Benzyl chloride Benzyl alcohol (iii) Ethyl magnesium chloride Propan1ol. (iv) Methyl magnesium bromide 2Methylpropan2ol.

Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.

How is 1propoxypropane synthesised from propan1ol Write mechanism of this reaction.

Explain the fact that in aryl alkyl ethers (i) The alkoxy group activates the benzene ring towards electrophilic substitution and (ii) It directs the incoming substituents to ortho and para positions in benzene ring.

When 3methylbutan2ol is treated with HBr, the following reaction takes place CHCHCHCH II CH, OH HBr Br CH CCH CH3 CH3 Give a mechanism for this reaction. (Hint The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by a hydride ion shift from 3rd carbon atom.

When active metals such as magnesium are immersed in acid solution, hydrogen gas is evolved. Calculate the work, in J, done by the reaction of 415 mL of 0.725 M HCI solution with excess Mg to give hydrogen gas and aqueous magnesium chloride at STP. Mg (s) 2 HCI (aq) H (9) MgCl (aq)

Bond angle in PH is higher than that in PH,. Why

What happens when H,PO,is heated

Why is HO a liquid and HS a gas

How is O,estimated quantitatively

Comment on the nature of two SO bonds formed in SO,molecule. Are the two SO bonds in this molecule equal

Write the conditions to maximize the yield of HSO,by Contact process.

How is nitrogen prepared in the laboratory Write the chemical equations of the reactions involved.

The HNH angle value is higher than HPH, HASH and HSbH angles. Why Hint Can be explained on the basis of sphybridisation in NH,and only sp bonding between hydrogen and other elements of the group.

Explain why NH,is basic while BiH,is only feebly basic.

Write main differences between the properties of white phosphorus and red phosphorus.

Justify the placement of O, S, Se, Te and Po in the same group of the periodic table in terms of electronic configuration, oxidation state and hydride formation.

Knowing the electron gain enthalpy values for O Oand 0 0as 141 and 702 kJ molrespectively, how can you account for the formation of a large number of oxides having Ospecies and not O (Hint Consider lattice energy factor in the formation of compounds).

Describe the manufacture of HSO.by contact process

How is SOan air pollutant

Why are halogens strong oxidising agents

What inspired N. Bartlett for carrying out reaction between Xe and PtF,

What are the oxidation states of phosphorus in the following,(i) H,PO, (ii) PCI, (iii) Ca,P (iv) Na,PO. (v) POF,

How are xenon fluorides XeF, XeF,and XeF,obtained

Arrange the following in the order of property indicated for each set (i) F2, Cl, Br2, 12 increasing bond dissociation enthalpy. (ii) HF, HCI, HBr, HI increasing acid strength. (iii) NH, PH,, ASH,, SbH,, BiH, increasing base strength.

Give the formula and describe the structure of a noble gas species which is isostructural with ICI (1) IBr, (ii) (iii) Bro

Why do noble gases have comparatively large atomic sizes

Classify the following solids in different categories based on the nature of intermolecular forces operating in them Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphide, graphite, rubidium, argon, silicon carbide.

Distinguish between (i)Hexagonal and monoclinic unit cells (ii) Facecentred and endcentred unit cells.

Explain how much portion of an atom located at (i)corner and (ii)bodycentre of a cubic unit cell is part of its neighbouring unit cell.

A compound forms hexagonal closepacked structure. What is the total number of voids in 0.5 mol of it How many of these are tetrahedral voids

A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 13rd of tetrahedral voids. What is the formula of the compound

An element with molar mass 2.7 x 10 kg molforms a cubic unit cell with edge length 405 pm. If its density is 2.7 x 103 kg m, what is the nature of the cubic unit cell

How can you determine the atomic mass of an unknown metal if you know its density and the dimension of its unit cell Explain.

Stability of a crystal is reflected in themagnitude of its melting point. Comment. Collect melting points of solid water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules

How will you distinguish between the following pairs of terms (i) Hexagonal closepacking and cubic closepacking (ii) Crystal lattice and unit cell (iii) Tetrahedral void and octahedral void

Calculate the efficiency of packing in case of a metal crystal for (i) simple cubic (ii) bodycentred cubic (iii) facecentred cubic (with the assumptions that atoms are touching each other).

Silver crystallises in fcc lattice. If edge length of the cell is 4.07 x 10 cm and density is 10.5 g cm, calculate the atomic mass of silver.

A cubic solid is made of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body centre. What is the formula of the compound What are the coordination numbers of P and Q

Niobium crystallises in bodycentred cubic structure. If density is 8.55 g cm, calculate atomic radius of niobium using its atomic mass 93 u.

If the radius of the octachedral void is r and radius of the atoms in close packing is R, derive relation between r and R.

Copper crystallises into a fcc lattice with edge length 3.61 x 10 cm. Show that the calculated density is in agreement with its measured value of 8.92 g cm.

Analysis shows that nickel oxide has the formula Ni09801.00 What fractions of nickel exist as Niand Niions

Ferric oxide crystallises in a hexagonal closepacked array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.

Gold (atomic radius 0.144 nm) crystallises in a facecentred unit cell. What is the length of a side of the cell

In terms of band theory, what is the difference (i) Between a conductor and an insulator (ii) Between a conductor and a semiconductor

Carboxylates substituents reaction. should contain electrondonating to undergoes an elimination Select one True False

Problem 1. Provide mechanisms for the following related transformations. R PPH3, CBR4 R R. Me H Me OH PPH3, CBr4 R. Me Me Br Br Br

QUESTION FOUR 20 MARKS (a) Describe technologies that are used to control emissions from internal combustion engines. 5 Marks 6 Marks 4 Marks (b) Discuss three technologies that are used for disinfection of drinking water. (c) Discuss the sources and health effects of mercury.

QUESTION THREE 20 MARKS (a) Describe the chemical processes for particle formation in the atmosphere. (b) Discuss the sources and health effects of indoor air pollutants. (c) Discuss the major stages in the treatment of wastewaters. 3 marks 5 Marks 7 Marks

n

The standard exam page is 8.50 inches by 11.0 inches. Its area in cm is a. 93.5 d. b. 603. e. C. 19.5 237. 36.8

Aluminium crystallises in a cubic closepacked structure. Its metallic radius is 125 pm. (i) What is the length of the side of the unit cell (ii) How many unit cells are there in 1.00 cmof aluminium

QUESTION ONE 15 MARKS AH (a) The for dissociation of molecular oxygen to atomic 020 AH 498.4 kjmol (1) Calculate the longest wavelength, in nanometers, that can dissociate Marks 0 oxygen is (c) Discuss ozone depletion and formation of ozone holes in the Antarctica regions. (d) Explain the health and environmental effects of UVB radiation. (e)

Calculate the equilibrium concentration of FeSCN2+ if 100 mL of 0.24 M Fe(NO3)3 are mixed with 100 mL of .24 M KSCN.

The lift cage in Figure No2 is hoisted by means of a rope wound round a 0.344 m diameter drum. The number of teeths per gear are Gear Nel is 20. Gear Ne3 is 25, Gear Ne4 is 75. Gear Ne5 is 35. Gear Ne7 is 105. The torque provided by motor to Gear Nel is 180 Nm. Find The holding torque if the efficiency of gear box is 75. Mass of lift cage that can

This problem will involve deriving a formula or two for a projectile launched from one height and angle and landing at a different height on Earth. Begin with a projectile launched at angle 0 above horizontal from a height y with initial velocity vo. The projectile lands at a point with height y. These are the given quantities v, 0, y, Y2 and g.

An experiment with three replications was conducted to test the concentration of three heavy metals in plant tissues of one plant species collected from three dumpsites. The data on heavy metal concentration are given below Dumpsite Kangoki Kisumu Nanyuki (a) (b) Block 1 2 3 12 2 3 1 2 3 Pb 6.6 6.5 6.7 6.8 6.9 6.9 7.0 7.1 7.1 Cd 6.5 6.5 6.6 7.0

A particle moves on xy plane according to equations x(t) 2t 3t y(t) t 4 (Take g10 ms. Please mark the closest answer as correct answer) Find the angle between acceleration and position vectors at t1 (a) 91.8 (b) 15.5 (c) 6,9 (d)84.9 (e) 18.1

If NaCl is doped with 10 mol of SrCI2, what is the concentration of cation vacancies

Describe Quantum numbers and their Properties b) An electron is in the fourth orbital s give the four sets of quantum numbers to describe the electron. (c) klhat are redox reactions distinguishing the differences between oxidation and reduction.

Calculate the pOH from the pH of 6.85 ?

In a certain chemical reaction Compound A combines with Compound B to produce Compound C (and no other products). Measurements were taken of the amounts of A and B present before and after a reaction that produced some C Compound A B initial amount 3.0 g 2.5 g final amount og 1.8 g,Calculate the theoretical yield of C. Round your answer to the

If the AH 145 kJmol and AS 94 JK mol for a nonspontaneous reaction, at what temperature does this reaction become spontaneous Your Answer Answer units

The correct order of radii is A. N < Be < B B. F < O 2- < N 3- C. Na < Li < K D. Fe 3+ < Fe 2+ < Fe 4+

Using the average bond enthalpy data given in the table below, calculate the mass of compound 1 required to heat 100 g of water by 35C. To get credit, you must show your work in full. You can assume that all heat losses are negligible. HO CC CH OH OH CO OO CO HO OH OH Table about the average bond enthalpies of selected bonds Types of bonds Average

Which of the following has the maximum number of unpaired electrons? (A) Mg 2+ (B) Fe2 + (C) Ti 3+ (D) V3 +

Among the following, O, Cl, F, N, P, Sn, Tl, Na, Ti The number of elements showing only one non zero oxidation state is.

The statement that is not correct for periodic classification of elements is. A. The properties of elements are the periodic functions of their atomic numbers B. Nonmetallic elements are less in number than metallic elements. C. For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals. D. The

Write the stepwise mechanism to predict the product(s) for the following reaction. Soc

Put the following in order of increasing Basicity 1. 2.

Calculate the concentration of nitric acid in moles per litre in a sample which has a density, 1.41 g mL 1 and the mass per cent of nitric acid in it being 69%. ?

Calculate the mass of sodium acetate (CH 3 COONa) required to make 500 mL of 0.375 molar aqueous solution. Molar mass of sodium acetate is 82.0245 g mol 1 ?

Calculate the amount of carbon dioxide that could be produced when (i) 1 mole of carbon is burnt in air. (ii) 1 mole of carbon is burnt in 16 g of dioxygen. (iii) 2 moles of carbon are burnt in 16 g of dioxygen.

Determine the empirical formula of an oxide of iron which has 69.9% iron and 30.1% dioxygen by mass?

Why are we able to sip hot tea or milk faster from a saucer rather than a cup?

Why does a desert cooler cool better on a hot dry day?

Give Reasons Only A. Water at room temperature is a liquid. B. Naphthalene balls disappear with time without leaving any solid. C. We can get smell of perfume several metres away.

What are the factors which affect the rate of evaporation Explain.

Ice melts by absorbing heat. When it melts, its temperature remains the same. Where does the heat energy go

2 ml of dettol is added to a beaker containing 500 mL of water and stirred. State four observations that you can make.

Evaporation is called as A. Surface phenomenon B. Bulk phenomenon C. Both surface and the bulk phenomenon D. Unique phenomenon

Arrange the following in the increasing order of forces of attraction A. Water, air, sugar B. Salt, air, juice C. Oxygen, water, sugar D. Sugar, oil, air

Which is the correct statement A. conversion of solid into liquid is called sublimation. B. conversion of vapours into solid without passing through the liquid state is called sublimation. C. conversion of solid into vapours without passing through the liquid state is called vaporisation. D. conversion of vapours into solid without passing through

Which of the following would be an example of a miscible solution. a) NaCl (s) dissolved in water b) Organge juice dissolved in water c) CO2 (g) dissolved in water d) Sugar dissolved in water

100 mL of 1.5 M HCI has more particles in solution than 100 mL of 1.0 M CaCl True O False

Calculate the OH- ion concentration from the hydrogen ion concentration. [H+]= 2.5 x 10-4 M

What are the conditions for optical isomers

The gasoline in an automobile gas tank has a mass of 61.0 kg and a density of 0.750 g/cm3. What is its volume in cm3 ?

The colour of light absorbed by an aqueous solution of CuSO4 is (a) Orange-Red (b) Blue-Green (c) Yellow (d) Violet

Consider the following list of reagent Acidified K2Cr2O7, alkaline KMnO4, CuSO4, H2O2, Cl2, O3, FeCl3, HNO3 and Na2S2O3 The total number of reagents that can oxidise aqueous iodide is ?

Potassium dichromate when heated with concentrated sulphuric acid and a soluble chloride, gives brown-red vapours of: (a) CrO 3 (b) Cr 2 O 3 (c) CrCl 3 (d) CrO 2 Cl 2

The actinoids exhibit more number of oxidation states in general than the lanthanoids. This is because (a) the 5f orbitals extend further from the nucleus than the 4f orbitals (b) the 5f orbitals are more buried than the 4f orbitals (c) there is a similarity between 4f and 5f orbitals in their angular part of the wave function (d) the actinoids