Redox reactions are those reactions in which oxidation and reduction occur Simultaneously. A redox reaction is made up of two half reactions. In the first half reaction, oxidation takes place and in second half reaction, reduction occurs. Oxidation is a process in which a substance loses electrons and in reduction, a substance gains electrons. The substance which gains electrons is reduced and acts as an oxidising agent. On the other hand, a substance which loses electrons is oxidised and acts as a reducing agent.
(i) Which of the following is a redox reaction?

(ii) Identify the reaction in which H2 02 is acting as a reducing agent.

(iii) For the following reactions, identify the one in which H₂S acts as a reducing agent.

(iv) For the following reaction, identify the correct statement.
\(\mathrm{ZnO}+\mathrm{CO} \longrightarrow \mathrm{Zn}+\mathrm{CO}_{2}\)

(v) In the following reaction, which substance is reduced?
\(\mathrm{PbS}+4 \mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{PbSO}_{4}+4 \mathrm{H}_{2} \mathrm{O}\)

The acidic behaviour of acids is due to the presence of hydrogenil(H⁺)ions in them. They produce hydrogen ions in the presence of water. Water is a polar solvent and this property of water helps in weakening the bond between the ions and makes them soluble. Hence, acids and bases produce ions in aqueous solutions.
It may be noted that a dry Hel gas or a solution of hydrogen chloride in organic, nonpolar solvents like toluene or benzene do not show acidic properties. This is because hydrogen chloride does not undergo ionization in toluene.
The reason why Hel splits into H⁺ and CI^- ions in presence of water lies in the fact that water molecules, being polar, pull the H⁺ and Cl ^- ions apart and thus, the bond in Hel is broken

(i) Identify the wrong statement.

(ii) If the pH of a solution is 8, then its [H⁺] ion is

(iii) In terms of acidic strength, which one of the following is in the correct increasing order?

(iv) Which of the following compounds does not give H⁺ ions in aqueous solution?

(v) Four solutions labelled as P, Q, Rand Shave pH values 1, 9, 3 and 13 respectively.
Which of the following statements about the given solutions is incorrect?

Baking powder produces carbon dioxide on heating, so it is used in cooking to make the batter spongy. Although, baking soda also produces CO₂ on heating, but it is not used in cooking because on heating, baking soda produces sodium carbonate along with carbon dioxide. Sodium carbonate, thus, produced, makes the taste bitter. Baking powder is the mixture of baking soda and a mild edible acid. Generally, tartaric acid is mixed with baking soda to make baking powder. When baking powder is heated, NaHCO₃ decomposes to give CO₂ which makes bread and cake fluffy. Tartaric acid helps to remove bitter taste due to formation of sodium tartrate.
\(2 \mathrm{NaHCO}_{3}+ \ \ \mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{6} \quad \longrightarrow \quad 2 \mathrm{CO}_{2}+2 \mathrm{H}_{2} \mathrm{O}+\mathrm{Na}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}\)
Baking soda         Tartaric acid            Carbon dioxide               Sodium tartrate
(i) On passing excess CO₂ gas in aqueous solution of sodium carbonate, the substance obtained is

(ii) When sodium hydrogen carbonate is added to acetic acid, it evolves a gas. Which of the following statements are true about the gas evolved?
(I) It turns lime water milky
(II) It extinguishes a burning splinter
(III) It dissolves in a solution of sodium hydroxide
(IV) It has a pungent odour

(iii) Select the correct statement regarding sodium hydrogen carbonate.

(iv) Acetic acid was added to a solid X kept in a test tube. A colourless and odourless gas was evolved. The gas was passed through lime water which turned milky. It was concluded that

(v) Which of the following statements are correct regarding baking soda?
(I) Baking soda is sodium hydrogen carbonate
(II) On heating, baking soda gives sodium carbonate
(III) It is used for manufacture of soap
(IV) It is an ingredient of baking powder

The chemical reactivity of an element depends upon its electronic configuration. All elements having less than eight electrons in the outermost shell show chemical reactivity. During chemical reactions, atoms of all elements tend to achieve a completely filled valence shell. Metals are electropositive in nature. They have tendency to lose one or more electrons present in the valence shell of their atoms to form cations and achieve nearest noble gas configuration. The compounds formed by the transfer of electrons from one element to other are known as ionic or electrovalent compounds.
(i) The electronic configurations of three elements X, Y and Z are:
            X : 2                  Y: 2, 8, 7                     Z : 2, 8, 2
Which of the following is correct regarding these elements?

(ii) Element X reacts with element Y to form a compound Z. During the formation of compound Z, atoms of X lose one electron each whereas atoms of Y gain one electron each. Which of the following properties is not shown by compound Z?

(iii) Which of the following is correct representation of formation of magnesium chloride?

	(d) None of these

(iv) The electronic configuration of sodium ion is

(v)Which of the following represents an electropositive element?

A hydrocarbon (P) has the molecular formula C₁₀H₂₂.A hydrocarbon (Q) has two carbon atoms less than (P) and belong to the same homologous series. A hydrocarbon (R) has two carbon atoms more than (P) and belong to the same homologous series.
(i) What is the molecular formula of (Q)?

(ii) To which homologous series do the compound (P), (Q) and (R) belong?

(iii) What is the molecular formula of (R)?

(iv) Identify the correct statement about compounds (P), (Q) and (R).

(v) Compounds (P), (Q) and (R) are

The recurrence of properties of the elements after a certain regular intervals, when they are arranged in the increasing order of their atomic numbers, is called periodicity. There are a number of physical properties such as atomic size, metallic and non -metallic character, etc. which show periodic variation. In periodic table, various properties vary differently from moving left to right in a period and going down in a group. In a period, properties vary because from moving left to right in a period, number of shells remain same but valence electron increases by one number hence nuclear charge increases. In a group, on going down, number of valence shells increases while number of valence electrons remains same.
(i) From top to bottom in a group of the periodic table, the electropositive character of the element

(ii) Which element has the largest size in the second period?

(iii) Which of the following elements has three valence electrons?

(iv) In the periodic table, the metallic character of elements
(a) decreases from left to right and decreases down the group
(b) decreases from left to right and increases down the group
(c) increases from left to right and increases down the group
(d) increases from left to right and decreases down the group
(v) Which of the following increases along the period?

The small intestine is the longest part of the alimentary canal. It is a narrow tube of about 6 metres which lies coiled in the abdomen. The length of small intestine varies in different animals depending on the type of food they eat.
(i) Humans are not able to digest cellulose whereas they are able to digest starch due to

(ii) What will happen if the lining X shown in the figure of transverse section of gut is smooth instead of having such foldings?

(iii) Butter cannot be digested in the stomach as lipase and bile are(a) released in small intestine

(iv) Which of the following is a correct statement?
(a) Herbivores have shorter small intestine as they eat grasses
(b) Carnivores have larger small intestine as they eat meat
(c) Herbivores have larger small intestine as they eat grasses
(d) None of these
(v) Various types of movements are generated by the ______ layer of the small intestine.

Double circulation is a type of circulating system in which the blood passes through the heart twice before completing a full circuit of the body. Blood is pumped from the heart to the lungs and returns to the heart before being distributed to other organs and tissues of the body.
(i) The figure shows blood circulation in humans with labels A to D. Select the option which gives correct identification of label and functions of the part.

(a) B - Capillary- Thin without muscle layer and wall two cell layers thick
(b) C - Vein-Thin walled and blood flows in jerks/spurts
(c) D - Pulmonary vein-Takes oxygenated blood to heart, PO₂ = 95 mm Hg
(d) A - Artery-Thick walled and blood flows evenly
(ii) Incomplete double circulation is seen in

(iii) Which of the following animals shows double circulatory pathway?

(iv) The given figure is of circulatory system. Identify the labelled parts (A-D) from the list (I-VII).

(I) Pulmonary circulation  (II) Systemic circulation  (III) Superior vena cava  (IV) Inferior vena cava
(V) Aorta                           (VI) Veins and venules                  (VII)Arterioles and capillaries

(v) Select the option which properly represents pulmonary circulation in humans.
\(\text { (a) Left auricle } \frac{\text { Deoxygenated }}{\text { blood }}{\longrightarrow} \text { Lungs } \frac{\text { Oxygenated }}{\text { blood }} \text { Right ventricle }\)
\(\text { (b) Left auricle } \frac{\text { Oxygenated }}{\text { blood }}{\longrightarrow} \text { Lungs } \frac{\text { Deoxygenated }}{\text { blood }}{\longrightarrow} \text { Right ventricle }\)
\(\text { (c) Right ventricle } \frac{\text { Deoxygenated }}{\text { blood }}{\longrightarrow} \text { Lungs } \frac{\text { Oxygenated }}{\text { blood }} \rightarrow \text { Left auricle }\)
\(\text { (d) Right ventricle } \frac{\text { Oxygenated }}{\text { blood }}>\text { Lungs } \frac{\text { Deoxygenated }}{\text { blood }} \gg \text { Left auricle }\)

Spore formation, method of asexual reproduction is used by unicellular as well as multicellular organisms.Spores are microscopic units which could be air borne or are present in soil, etc.
(i) A slice of bread kept in open for sometime shows growing white cottony mass which later turns black. This happens because
(a) bacterial spores present in air germinate on the surface of bread slice
(b) fungal spores present in air germinate on the surface of bread slice
(c) protozoan microbes start feeding on bread slice
(d) none ef these.
(ii) Spore formation can be seen in

(iii) Bulb like structure at top of erect hyphae where spores are produced is

(iv) Select the incorrect statement.
(a) Spores can be produced endogenously or exogenously in an organism.
(b) Spores can be air borne or soil borne.
(c) Bacteria produce only exospores.
(d) Rhizopus bears spores in special structures called sporangium.
(v) Observe the given figure showing spores formation in Rhizopus and select the option which is correctly labelled.

(a) P-Stolon, S-Columella, T-Sporangiophore
(b) Q-Stolon, P-Hypha, S-Sporangium
(c) R-Sporangium, S-Apophysis, T-Sporangiophore
(d) Q-Stolon, R-Sporangium, S-Colume!la

Gregor Mendel conducted hybridisation experiments on garden peas for seven years and proposed the laws of inheritance in living organisms. He investigated characters in the garden pea plant that were manifested as two opposing traits, e.g., tall or dwarf plants, yellow and green seeds, etc.
(i) Among the seven pairs of contrasting traits in pea plant as studied by Mendel, the number of traits related
to flower, pod and seed respectively were

(ii) The colour based contrasting traits in seven contrasting pairs, studied by Mendel in pea plant were

(iii) Refer to the given table of contrasting traits in pea plants studied by Mendel.

Character	Dominant trait	Recessive trait
(i) Seed colour
(ii) Flower colour
(iii) Pod shape
(iv) Flower position

Which of the given traits is correctly placed?
(a) (i), (ii) and (iii) only
(b) (ii), (iii) and (iv) only
(c) (ii) and (iii) only
(d) (i), (ii), (iii) and (iv)
(iv) Some of the dominant traits studied by Mendel were
(a) round seed shape, green seed colour and axial flower position
(b) terminal flower position, green pod colour and inflated pod shape
(c) violet flower colour, green pod colour and round seed shape
(d) wrinkled seed shape, yellow pod colour and axial flower position.
(v) Which of the following characters was not chosen by Mendel?

A prism is a transparent refracting medium bounded by two plane surfaces inclined to each other at a certain angle. The refraction of light through a prism follows the laws of refraction. In the prism, refraction takes place on its refracting surface it means when the light enters the prism and when the light leaves the prism. The refraction through a prism is shown. Here, A is the angle of prism, \(\angle\)i is the angle of incidence of the face AB and \(\angle\)e is the angle of emergence at other face AC.

The incident ray suffers a deviation or bending through an angle \(\begin{equation} \delta \end{equation}\)  due to the refraction through prism. This angle is called angle of deviation as shown in figure.
\(\angle\)i + \(\angle\)e = \(\angle\)\(\begin{equation} \delta \end{equation}\) + \(\angle\)A
(i) The angle between the two refracting surfaces of a prism is called

(ii) The angle between the incident ray and the emergent ray is called

(iii) When a ray is refracted through a prism, then

(iv) The angle of deviation depends on

(v) The rectangular surfaces of a prism are known as

A magnetic field is described by drawing the magnetic field lines. When a small north magnetic pole is placed in the magnetic field created by a magnet, it will experience a force. And if the north pole is free, it will move under the influence of magnetic field. The path traced by a north magnetic pole free to move under the influence of a magnetic field is called a magnetic field line. Since the direction of magnetic field line is the direction of force on a north pole, so the magnetic field lines always begin from the N-pole of a magnet and end on the S-pole of the magnet. Inside the magnet, however the direction of magnetic field lines is from the S-pole of the magnet to the N-pole of the magnet. Thus, the magnetic field lines are closed curves. When a small compass is moved along a magnetic field line, the compass needle always sets itself along the line tangential to it. So, a line drawn from the south pole of the compass needle to its north pole indicates the direction of the magnetic field at that point.

(i) The magnetic field lines
(a) intersect at right angle to one another
(b) intersect at an angle of 45° to each other
(c) do not cross one another
(d) cross at an angle of 60° to one another.
(ii) A strong bar magnet is placed vertically above a horizontal wooden board. The magnetic lines of force will be
(a) only in horizontal plane around the magnet
(b) only in vertical plane around the magnet
(c) in horizontal as well as in vertical planes around the magnet
(d) in all the planes around the magnet.
(iii) Magnetic field lines can be used to determine
(a) the shape of the magnetic field
(b) only the direction of the magnetic field
(c) only the relative strength of the magnetic field
(d) both the direction and the relative strength of the magnetic field.
(iv) The magnetic field lines due to a bar magnet are correctly shown in figure

(v) Which of the following is not true about magnetic field lines?
(a) Magnetic field lines are the closed and continuous curve.
(b) No two field lines can cross each other.
(c) Crowdness of field lines represents the strength of magnetic field.
(d) The direction of field lines is from the north pole to the south pole inside a bar magnet.

Some harmful non-biodegradable chemicals, i.e., pesticides (e.g., DDT) and heavy metals (e.g., mercury, arsenic cadmium, etc.) enter the bodies of organism through the food chain and go on concentrating at each trophic level. This phenomenon is called bio-magnification or biological magnification.
(i) Refer to the given food chain
Phytoplankton \(\longrightarrow\) Zooplankton \(\longrightarrow\)Small fish \(\longrightarrow\) Large fish\(\longrightarrow\)Fish eating birds
If concentration of DDT in small fish is estimated to be 0.5 ppm, then amount of DDT in zooplankton and large fish would respectively be

(ii) Refer to the given table.

According to the given data. The correct order in a food chain will be

(iii) A group of scientists analysed samples of five different animals from a river for possible accumulation of DDT in their body due to bio-magnification. The result obtained is shown in the given graph.
The correct order of the food chain operating in a river is

(iv) Higher amount of DDT disturb calcium metabolism of birds. This results in

(v) When animals are sprayed with poisons, they may die immediately, but their bodies still contain the poison. The poison in their bodies will then be passed on to the animals which eat them. What would be the consequence of a mass poisoning of the rabbit population in a grazing food chain and why?
(a) Plants would die quickly as they are eaten by rabbits
(b) Grasshopper would die quickly as all the animals in the food web would be affected
(c) Western rattlesnakes would quickly become poisoned as they eat rabbits
(d) Hawk would become poisoned as they feed on rabbits

Various components of an ecosystem maintain a balance in nature. Disturbance in any component of the environment cause an imbalance. One of the main environmental problem caused by human activities is global warming. Global warming is a phenomenon caused by the increasing concentration of greenhouse gases in the atmosphere resulting due to enhanced greenhouse effect.
(i) Refer to the given pie chart showing the contribution of different gases to global warming.

Identify gases P, Q, Rand S and select the incorrect statement regarding them.
(a) P could be a gas that increases in atmosphere due to excessive use offossil fuel.
(b) Q could be a gas produced by complete combustion of biomass.
(c) R could be synthetic gaseous compounds used as refrigerants in air conditioners and refrigerators.
(d) S could be a gas produced by combustion of nitrogen rich fuel.
(ii) What could not be a source of gas Q given in the above pie chart?

(iii) If there is no CO₂ in the atmosphere, then what will be the most likely consequence of this on the temperature of earth?
(a) The temperature remain unchanged as it depends upon the oxygen content of the atmosphere.
(b) The temperature would increase as less greenhouse gases will be absorbed by CO₂
(c) The temperature would decrease as CO₂ is the principal greenhouse gas.
(d) None of these
(iv) Study carefully the following figure representing greenhouse effect.

Select the correct statement regarding this.
(a) Much of the long wavelength infrared radiations re-radiated by the earth's surface are absorbed by the atmospheric greenhouse gases.
(b) CO₂ , CH₄ , CFCs and N₂O are the gases which are responsible for greenhouse effect.
(c) The atmosphere is transparent to the incoming short-wavelength radiations and is translucent to the long-wavelength infra-red radiations.
(d) All of these

(v) Greenhouse effect is due to

Energy flow is the key function of an ecosystem. It is determined by the two basic laws of thermodynamics. Flow of energy in our ecosystem is unidirectional. Green plants capture approximately about 1% of the solar energy incident on the earth to carry out the process of photosynthesis. In an ecosystem, transfer of energy follows 10 percent law, i.e., only 10% energy is transferred from one trophic level to another and remaining 90% of energy is lost in respiration.
(i) Read the given statements and select the incorrect one(s).
I. At each trophic level organisms utilise energy in respiration.
II. Only 10 percent of the solar radiations that fall on earth is used by green plants.
III. Green plants are the ultimate source of entire energy as most of the food chain begin with them.
IV. A food chain usually consist of 3-4 trophic levels.

(ii) Refer to the given flow chart.
Plants \(\rightarrow\) Rat \(\rightarrow\) Snake
20 units   2 units   0.2 unit
The given flow chart states that
(a) flow of energy in an ecosystem is unidirectional
(b) as we move along in a food chain the number of individuals at each trophic level decreases
(c) only 10% of the total energy becomes available to next trophic level
(d) both (a) and (c).
(iii) Nearly 90% of the energy is wasted while moving from one trophic level to other. This energy is used in

(iv) Refer to the given pyramid.

Which of the following best explains the phenomenon?

(v) Which of the following correctly states the processes involved in energy transfer between the trophic levels?