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Chemistry Questions and Answers August 20, 2020

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When an object moves closer to convex lens, the image formed by it shift (a) away from the lens (b) towards the lens (c) first towards and then away from the lens (d) first away and then towards the lens

A magnified real image is formed by a convex lens when the object is at (a) F (c) 2F (b) between F and 2F (d) (a) and (b) both

A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is (a) 30 cm (c) 40 cm (b) 20 cm (d) 60 cm

Figure shows a ray of light as it travels from medium A to medium B. Refractive index of the medium B relative to medium A is NCERT Exemplar (b) 45 45 30 60 Medium B Medium A (d) 2

Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively as shown in the figure. Which of the following could be inside the box NCERT Exemplar (a) A rectangular glass slab (b) A convex lens. (c) A concave lens (d) A prism A B Box

A beam of light is incident through the holes on side A and emerges out of the hole on the other face of the box as shown in the figure. Which of the following could be inside the box NCERT Exemplar A B 10 olo 9 8 7 6 5 4 3 2 1 (a) Concave lens (b) Rectangular glass slab (c) Prism (d) Convex lens Box 7000

Which of the following statements isare true (a) A convex lens has 4 dioptre power having a focal length 0.25 m (b) A convex lens has 4 dioptre power having a focal length 0.25 m (c) A concave lens has 4 dioptre power having a focal length 0.25 m (d) A concave lens has 4 dioptre having a focal length 0.25 m

Magnification produced by a rear view mirror fitted in vehicles (a) is less than one (b) is more than one (c) is equal to one (d) can be more than or less than one depending upon the position of the object in front of it.

A full length image of a distant tall building can definitely be seen by using NCERT Exemplar (a) a concave mirror (b) a convex mirror (c) a plane mirror (d) both concave as well as plane mirror

The laws of reflection hold good for (a) plane mirror only (b) concave mirror only (c) convex mirror only (d) all mirrors irrespective of their shape

The path of a ray of light coming from air passing through a rectangular glass slab traced by four students are shown as A, B, C and D in figure. Which one of them is correct (a) A (a) (C) (b) B (c) C (b) (d) (d) D

In which of the following, the image of an object placed at infinity will be highly diminished and point sized (a) Concave mirror only (b) Convex mirror only (c) Convex lens only (d) Concave mirror, convex mirror, concave lens and convex lens.

When light falls on a smooth polished surface, most of it (a) is reflected in the same direction (c) is scattered (b) is reflected in different directions (d) is refracted into the second medium

Image formed by reflection from a plane mirror is (a) real and inverted (c) real and erect (b) virtual and erect (d) virtual and inverted

If an incident ray passes through the focus, the reflected ray will (a) pass through the pole (c) retrace its path (b) be parallel to the principal axis (d) pass through the centre of curvature

Focal length of a concave mirror is (a) negative (c) depends on the position of object (b) positive (d) depends on the position of image

If the power of a lens is 2 D, what is its focal length (b) 100 cm (a) 50 cm (c) 50 cm (d) 100 cm

When the object is placed between fand 2f of a convex lens, the image formed is (a) at f (b) at 2f (c) beyond 2f (d) between O and f

Monochromatic light of frequency 5 x 104 Hz travelling in vacuum enters a medium of refractive index 1.5. Its wavelength in the medium is (a) 5000 (b) 4000 (c) 5500 (d) 6000

Two thin lenses, one of focal length 60 cm and the other of focal length 20 cm are kept in contact. Their combined focal length is (a) 30 cm (b) 30 cm (c) 15 cm (d) 30 cm

When light travels from one medium to other whose refractive index is different, then which of the given will change (a) Wavelength and velocity (c) Frequency and wavelength (b) Frequency and wavelength (d) Frequency, wavelength and velocity

The number of images observable between two parallel mirrors is (a) 2 (d) Infinity (b) 4 (c) 6

A hole is made in a convex lens, then (a) A hole appears in the image (c) Image intensity decreases (b) Image size decreases (d) No change

Which of the given is not true of an image formed by a plane mirror (a) It is erect (b) It is virtual (c) It is diminished (d) It is at the same distance as the object

Two lenses of power 3 and 1 dioptres are placed in contact. The focal length of the combined lens is (a) 100 cm (b) 25 cm (c) 50 cm (d) 30.3 cm

The focal length of a concave mirror is 50 cm. To obtain an inverted image two times the size of the object, the object should be placed at (a) 50 cm (b) 63 cm (c) 72 cm (d) 75 cm

The focal length of lens depends on (a) The radii of curvature of its surfaces (b) The refractive index of its material (c) The refractive index of the medium surrounding (d) All of these factors

A parallel beam of light is incident on a converging lens parallel to its principal axis. As we move away from the lens on the other side on its principal axis, the intensity of light (a) Remains constant (b) Continuously increases (c) Continuously decreases (d) First increases and then decreases

Using a convex lens, a clear image of candle flame is produced on a screen. How many other clear images can be received on this screen if only the lens is to be shifted (a) A large number (b) Only one more (c) Two more (d) None of these

A convex lens of power P is immersed in a water. How will its power change (a) Increases (b) Remain unchanged (c) Decreases (d) Increases for red colour and decreases for blue colour

Which of the given can produce a virtual image larger in size than the object (a) Concave lens (b) Convex lens (c) Convex concave lens (d) None of these

A lens has a power of 0.5D. It is (a) A concave lens of local length 5 m (c) A convex lens of focal length 5 m (b) A convex lens of focal length 2 m (d) A concave lens of focal length 2 m

Refractive index (a) Depends on the wavelength of light used (b) Is actual property of the substance (c) Depends on the angle of incidence (d) None of these

Which of the given is NOT paired correctly (a) Solar furnaceconcave mirror (c) Magnifying glass convex lens (b) Rearview mirrorconvex mirror (d) None of these

In order to obtain a magnification of, 0.6 (minus 0.6) with a concave mirror, the object must be placed (a) At the focus (b) Between pole and focus (c) Between focus and centre of curvature (d) Beyond the centre of curvature

Which statement is true for the reflection of light (a) The angle of incidence and reflection are equal. Q (b) The sum of angle of incidence and reflection is always greater than 90. (c) The reflected light is less bright than the incident light. (d) The beams of incident light after reflection diverges at unequal angles.

The image shows reflection of light on a mirror. Incident ray Normal 0 0 Reflecting surface Reflected ray,Based on the image, what can be inferred CBSE Question Bank (a) The angle between incident ray and normal is greater than the angle between normal and the reflected ray. (b) The incident ray, the normal to the mirror at the point of incidence

The image shows the path of incident rays to a concave mirror. Object Where would the reflected rays meet for the image formation to take place (a) Between F and O (c) Between C and F (b) Beyond C (d) Behind the mirror CBSE Question Bank

An object is placed near a concave mirror at a distance of onefourth the radius of curvature of the concave mirror. Which ray diagram shows the incident rays, reflected rays, and the position and nature of the image formed CBSE Question Bank (a) (b) (c) Image Object Object P Principal axis (d) Image at B Object at A 8 O B

Which image represents the path of incident and reflected ray from a convex mirror when an object is placed at infinity CBSE Question Bank (a) Incident ray Reflected ray Object at infinity P F Convex mirror,(c) (d) Incident ray Z Object at infinity Incident ray Z Object at infinity Incident ray Z Object at infinity Reflected ray P Reflected ray

A student studies that convex mirror always forms virtual image irrespective of its position. What causes the convex mirror to always form a virtual image CBSE Question Bank (a) Because the reflected ray never intersect. (b) Because the incident ray traces its path back along the principal axis. (c) Because the incident ray of a convex mirror gets

A student conducts an activity using a concave mirror with focal length of 10 cm. He placed the object 15 cm from the mirror. Where is the image likely to form CBSE Question Bank (a) At 6 cm in front of the mirror (b) At 6 cm behind the mirror (c) At 30 cm behind the mirror (d) At 30 cm in front of the mirror

The image shows the path of light travelling through a glass slab. Medium 1 B P E N Medium 2 Air N M 1 102 Glass Q R Lateral Shift What causes the ray of light to deviate from its original path (a) Change in the temperature of the air (b) Change in the amount of light (c) Change in the direction of wind flow (d) Change in the density of the

A student studies that speed of light in air is 300000 kmsec whereas that of speed in a glass slab is about 197000 kmsec. What causes the difference in speed of light in these two media CBSE Question Bank (b) Difference in amount of light (d) Difference in temperature (a) Difference in density (c) Difference in direction of wind flow

The speed of light in air is 3 x 10 ms, whereas that of the speed of light in water is 2.26 x 108 ms. What is the refractive index of water with respect to air CBSE Question Bank (a) 2.64 (b) 1 (c) 1.32 (d) 0.75

A student conducts an experiment using a convex lens of focal length 20 cm and an object of height 15 cm. He placed the object at 25 cm from the lens. Can the image be formed on a screen CBSE Question Bank (a) Yes, because a real image will be formed. (b) Yes, because an erect image will be formed. (c) No, because an inverted image will be formed.

An image of an object is produced on a screen which is about 36 cm using a convex lens. The image produced is about 3 times the size of the object. What is the size of the object CBSE Question Bank (a) 12 cm (b) 12 cm (c) 33 cm (d) 39 cm

An object of height 10 cm is placed in front of a convex lens having focal length of 12 cm. The object is placed at a distance of 36 cm in front of the lens. How many times is the image likely to be magnified (a) times (b) 3 times (c) 4 times (d) 2 times

A student conducts an experiment using a convex lens. He places the object at a distance of 60 cm in front of the lens and observed that the image is formed at a distance of 30 cm behind the lens. What is the power of the lens CBSE Question Bank (a) 0.005 dioptre (b) 50 dioptre (c) 5 dioptre (d) 0.05 dioptre

Please use line structure when doing this mechanism. 12. Use electron pushing arrows to show the mechanism for the reaction 3methyl2pentene and hydrogen chloride. Identify intermediates and the rate determining step and be sure to include the structure of the product. 6

What is the pH of 0.001M HCl?

What is the pOH of 0.02M NaOH?

Determine the pH of 0.05M KOH

Determine the pOH of 0.03M HCl

Determine the hydrogen ion concentration of HNO3 with pH of 3

Determine the hydroxide ion concentration of NaOH with pH of 3.5

Determine the pH of 0.3M H2SO4

Define pH. Hence, differentiate between pH and pOH

Pure water is said to have a pH of ______

Calculate the pH of a buffer containing 0.2M sodium acetate and 0.25M acetic acid (pKa = 4.76)

If the pH of potassium acetate-acetic acid buffer is 4.9, determine the mole ratio of salt/acid. (pKa = 4.76)

Determine the change in pH on addition of 0.02M NaOH to a buffer containing 0.3M sodium acetate and 0.15M acetic acid. (pKa = 4.76)

A buffer is prepared by mixing 50ml of 0.3M phosphoric acid and 100mL of 0.25M sodium phosphate. Determine the pH of the buffer. (pKa = 2.12)

Draw the molecule(s) on the canvas by choosing buttons from the Tools (for bonds), Atoms, and Advanced Template toolbars. The single bond is active by default. DOCQQQ H hal H C N O Hovaw 1 Constants 1 Periodic Table S C

How old is a piece of wood that has 0.7813 of the carbon14 of a living organism Express your answer numerically in years using four significant figures. Do not include a comma in the answer View Available Hint(s) Submit Provide Feedback C years MA P W Pr

For which of the following mixtures will Ag2SO4(s) precipitate? 150.0 mL of 0.10 M Na2SO4(aq) and 5.0 mL of 0.20 M AgNO3(aq) 150.0 mL of 0.10 M Na2SO4(aq) and 5.0 mL of 0.30 M AgNO3(aq) 150.0 mL of 0.10 M Na2SO4(aq) and 5.0 mL of 0.40 M AgNO3(aq) 150.0 mL of 0.10 M Na2SO4(aq) and 5.0 mL of 0.50 M AgNO3(aq)

Draw the main organic product for the reaction shown. O 1. LiAlH4, EtO 2. HO Select Draw Rings More H O,Draw the organic product for the reaction shown. Omit any inorganic byproducts or ions. NH 1. LIAIH4 2. HO Select Draw Rings H N More O
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Draw Lewis structure(s) showing all possible equivalent resonance forms for the nitryl chloride molecule (NOCI). Draw one structure per sketcher box, and separate any added sketcher boxes with the bonds to oxygen unless they are needed for the central atom to obey the octet rule. NOCl symbol. Do NOT show any ion charges in your drawings. Do not
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The oxidation number of Cl in ClO4? isAnswers? 1. +1. +3. +5. none of these.

KSO4 has a vant Hoff factor of i 2.6. What is the concentration of particles in a 1.0401 M solution of K2SO4 M
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Is it true that a method of handpicking can be used to remove small pebbles or dirt particles from a given sample of pulses before cooking? Options: True False

Is it true that a mixture of sand and water can be separated by the process of sedimentation and decantation? Options: True False

Burning of wood and coal causes Options: Pollution of air Pollution of water Pollution of soil Pollution in space

Question 44): Is it true that particles larger than 2.0 mm are called gravel or stones? Options: True False

The method/s used to obtain salt from sea water is/ are Options: Sedimentation Decantation Filtration Evaporation

Two naturally obtained fibres is/are Options: 1) Nylon and polyester 2) Rayon and acrylic 3) Cotton and silk 4) Dacron and polypropylene

The part of silk making process that is/ are considered as being cruel by animal rights activists is Options: Weaving Dyeing Thread extraction Spinning

The fibre/s that is/are made from chemicals obtained from petroleum are called Options: Cotton fibre Jute fibre Silk fibre Synthetic fibres

Which of these fabrics will you choose to wear in hot and humid conditions? Options: Cotton Silk Nylon Wool

Historians believe that cotton clothes were first worn in Options: 1) India 2) Egypt 3) China 4) Europe

Which of these is/are not a property of jute? Options: Biodegradability Durability Smoothness Strength

The property which is common to all matter is/are Options: Matter takes up space and has no mass. Matter can be seen and has some mass. Matter takes up space and has mass Matter takes up space and may or may not have mass.

Wearing many layers of cotton keeps you warm because Options: Many layers will produce heat together. Trapped air acts as an insulator between layers. Cotton retains moisture. Cotton evaporates absorbed moisture.

The correct sequence of steps involved in the process of making woollen clothes is/are Options: Shearing > Scouring > Transportation > Combing > Spinning > Weaving / Knitting. Shearing > Scouring > Transportation > Spinning > Combing > weaving / Knitting. Transportation > Spinning > Combing > Shearing > Scouring > Weaving / Knitting. Weaving /

For a given cell , the electrode potential of the cathode and anode are +0.80 and -0.25 respectively, then the emf of cell is : A) +0.55 V B) -0.55 V C) -1.05 V D) +1.05 V

In an aqueous solution , the cation of salt is found to be twice as fast as anion . Then transport number of cations A) 0.11 B) 0.33 C) 0.66 D) 0.22

The specific conductance of 0.1M NaCl solution is 1.06*10-2mhos cm-1. the molar conductance is : A) 1.02*102 B) 1.02*104 C) 1.02*104 D) 53

Number of triple points in the phase diagram of Sulphur is : A) 1 B) 2 C) 3 D) 4

An aqueous solution of ferric chloride is : A) Neutral B) Acidic C) Basic D) Amphoteric

4 gram of NaOH is dissolved in 1 Lwater. The pH of solution is : A) 4 B) 13 C) 1 D) 14

A catalyst increases reaction rate by: A) Increasing activation energy B) Increasing entropy C) Decreasing entropy D) Decreasing activation energy

The concentration of a reactant isdoubled and the rate is increased by a factor4.the order of reaction is : A) 0 B) 1 C) 2 D) 3

The molar enthalpy of reactionN2+3H2 converted to 2NH3is xkJ. The molar enthalpy offormation of ammonia is : A) x kJ B) x/2 kJ C) 2x kJ D) 4 kJ

The efficiency of Carnot engine operating between 27 degree Celsius and 227 degree Celsius is : A) 0.9 B) 2.5 C) 0.4 D) 0.5

which of the following process isaccompanied by a decrease in entropy? A) Condensation of steam B) Burning of kerosene C) Evaporation of water D) Dissolution of sugar in water

Identify the intensive properties A) Enthalpy and temperature B) Volume and temperature C) Enthalpy and volume D) Temperature and density

Pyrrole can be prepared by A) Hawarth synthesis B) Paal-Knorr synthesis C) Killiani synthesis D) Kolbes method

Carbohydrates which differ instereochemistry at one asymmetric centre are known as : A) Epimers B) Conformers C) Isomers D) diastereomer

An acid which does not contain COOHgroup is : A) Ethanoic acid B) Succinic acid C) Picric acid D) Palmitic acid ( picric acid is trinitrophenol)

Aldehyde can be converted tohydrocarbon by : A) Rosemont reduction B) Cannizaro reaction C) Clemmenson reduction D) Sanmeyer reaction