Periodic Test Paper (pre, Mid, Post)

HCl is oxidized, and MnO₂ is reduced.

HCl is oxidized to chlorine as hydrogen is removed and removal of hydrogen is oxidation.

MnO₂ is reduced to MnCl₂ as oxygen is removed and removal of oxygen is called reduction. So we can say HCl is oxidized to chlorine and MnO₂ is reduced to MnCl₂.

Haemoglobin is the pigment which transports oxygen and carbon dioxide in the human body.

Oxygen combines with hemoglobin forming oxy-hemoglobin and is transported inside our body.

Hemoglobin can carry a very small quantity of carbon dioxide in the form of carbamino-hemoglobin.

Haemoglobin is a respiratory pigment found in RBCs which helps in transport of respiratory gases.

SI unit of resistivity is ohm meter.

As we know

Here ρ is resistivity, R is resistance, l is length, A is the cross-sectional area.

Here unit of resistance is ohm, cross-section area unit is m²; length unit is m.

ρ = ohm.m

So the unit of ρ is ohm.m.

No change will be observed on the spoon as well as in the solution. Silver is less reactive than copper as it is placed below copper in metal activity series. So silver cannot displace copper from its salt solution. Hence no changes are observed.

Fig showing metal activity series.

Silver chloride gets decomposed by sunlight. Sunlight contains photons- a source of energy which decomposes silver chloride to silver and chlorine.

2AgCl(s) → 2Ag(s) + Cl₂ (g)

So to protect from the decomposition of silver chloride by sunlight, they are stored in dark coloured bottles.

As the chemical reaction occurs in the presence of sunlight, so the reaction is known as photochemical reactions. It is an example of the photochemical decomposition reaction.

a. Trypsin acts upon peptides and converts to amino acids. So substrate is peptides.

Peptides are proteins, and trypsin is present in pancreatic juice secreted by the pancreas. It converts peptides into amino acids which are simplest forms of proteins.

b. Amylase acts upon starch.

It converts starch into maltose. Amylase is present in saliva secreted by salivary glands present in the mouth. It is also present in pancreatic juice.

c. Pepsin acts upon proteins.

Pepsin is present in gastric juice secreted by gastric glands present in the stomach. It acts upon proteins to convert into peptides.

d. Lipase acts upon emulsified fats/lipids.

Lipase is present in pancreatic juice. It acts upon emulsified fats to convert them into fatty acids and glycerol. Emulsified fats mean large fat globules are converted into small fat droplets, and this emulsification process is done by bile juice secreted from the liver.

Here P =18 W

As resistor A is in series with the parallel combination of resistors B and C, so it carries maximum current.

We know P = I²R

I² = 9

I = 3 A

If I_B and I_C are current flowings through resistor B and C respectively and the potential difference will be same across both resistors B and C as they are connected in parallel.

So we know V = IR

I_BR_B = I_CR_C

So

I_B = I_C

But I = I_B + I_C

3 = 2I_B [ since I_B = I_C]

I_B = 3/2

I_B = 1.5 A

I_C = 1.5 A

So maximum current flows through resistor A is 3 A, B is 1.5 A and C is 1.5 A.

Fuse wire is a safety device connected in an electric circuit in a series connection with the live wire. It has high resistivity and low melting point so that it would allow current up to its safe limit to pass through it, but if excess current flows it will melt and blows off thus breaking the circuit and prevent any hazards from short-circuiting and it also prevents the costly electrical appliances like geyser, toaster, microwave, etc. from getting damaged.

a.Na₂CO₃ + HCl → NaCl + NaHCO₃

When sodium carbonate reacts with HCl in equal molar concentration, sodium chloride and sodium hydrogen carbonate are produced.

b.NaHCO₃ + HCl → NaCl + H₂O + CO₂

When sodium hydrogen carbonate reacts with HCl, it gives sodium chloride, water, and carbon dioxide gas.

c.2CuSO₄ + 4KI → Cu₂I₂ + I₂ + 2K₂SO₄

When copper sulphate reacts with potassium iodide, iodine gas is liberated along with the formation of potassium sulphate and cuprous iodide precipitate.

a. Ventricles pump blood to long distances for example- right ventricle pumps blood to lungs for oxygenation and left ventricle pumps blood to the whole body. So walls of ventricles are thicker as they have to pump blood to long distance, so they contract more and have to withstand more pressure.

b. Breathing cycle is rhythmic which involves inhalation and exhalation of air. But the exchange of gases is a continuous process which takes place in alveoli between blood capillaries and air sacs. Even though after forceful exhalation, some residual air is left inside air sacs, so the exchange of this air takes place between air sacs and blood capillaries. Since cells continuously take in oxygen for oxidation of glucose to release energy and carbon dioxide is given out hence exchange of gases occurs continuously.

c. During day time, green plants perform photosynthesis so the carbon dioxide produced in respiration is used by green plants for photosynthesis. As carbon dioxide is an important raw material for photosynthesis process. So in green plants during the day carbon dioxide is generated in respiration but is not released out.

a. V across point BC = ?

I = 1 A

R_p = 6 ohm [derived in c. below]

So V = IR

= 6A × 1Ω

V = 6 ohm

I₁ =

I₁ =

I₁ = 0.6 A

Similarly I₂ =

I₂ =

I₂ = 0.4 A

b. I = 1 A

R = 5 ohm

So V across AB = ?

We know V = IR

V = 5A × 1Ω

V = 5 V

V across AC = ?

Total R = 11 ohm [derive in c. below]

V = 1 × 11

V = 11 V

c. Total resistance = ?

Resistors R1 and R2 are in parallel

So

R_p = 6 ohm

Total R = 5 ohm + 6 ohm

R = 11 ohm

a. 2Cu(NO₃)₂ (s) → 2CuO(s) + 4NO₂(g) + O₂(g)

On heating copper(II) nitrate powder, copper oxide, oxygen gas and nitrogen dioxide gas is evolved.

b. Brown gas X is nitrogen dioxide NO₂.

c. It is a decomposition reaction as a single reactant splits on heating to form two or more products. Since heat is involved so we can also say it is a thermal decomposition reaction.

d. X is nitrogen dioxide which is a acidic gas so its aqueous solution will be acidic in nature and its pH would be less than 7. Since the acid pH varies between 0-7.

Nitrogen dioxide with water forms nitrous acid(HNO₂)

Urine formation occurs in three steps:

a. Ultrafiltration: Blood containing nitrogenous wastes flows with a great pressure through the glomerulus. The liquid portion of the blood gets filtered through glomerulus and collects in the Bowman’s capsule which is called glomerular filtrate. This process is called ultrafiltration.

b. Selective reabsorption: The glomerular filtrate contains a lot of useful substances like glucose, water, salts, etc. which gets selectively reabsorbed by different parts of the renal tubule. This process is called selective reabsorption.

c. Tubular secretion: Distal convoluted tubule part of nephron secretes some harmful substances like salts, antibiotics like penicillin etc. to the forming urine which is called tubular secretion.

The formed urine is then received by collecting ducts which pours into the pelvis of kidney.

a. i. Electric lamp works on the principle of the heating effect of electric current, so when current passes through the filament of bulb, a large amount of heat is produced making the filament of the bulb to emit light. So the temperature rises to a maximum value, and the material of filament should be such that it can withstand maximum temperature without melting. So tungsten is used as it has a high melting point of 3380^oC, hence it is used exclusively for the filament of electric lamps.

ii. Copper and aluminum are metals so they have free electrons present in them which makes them good conductors of electricity. Their resistivity is also very low so they are employed for the transmission of electricity.

b. 1. Three resistors R_1, R_2, R₃ are connected in parallel as shown in the diagram below. A battery, key, ammeter, voltmeter is connected.

2. Key is plugged in and ammeter, voltmeter readings are noted down.

3. Then key is taken out along with ammeter and voltmeter.

4. Ammeter is connected in series and voltmeter in parallel with resistor R_1. Readings are noted down.

5. Above step is repeated for resistor R₂ and R_3.

6. Readings are noted for three resistors it would be found that ammeter readings for three resistors are different but voltmeter readings are same.

This proves that potential difference is same across three resistors connected in parallel since voltmeter measures the potential difference across resistors.