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Relative density = \(\frac{density\,of\,liquid}{density\,of\,water}\)

∴ Density of liquid = Relative density x density of water

= 1.25 × 1000 = 1250 kg/m³

The reading will be 1 When dipped in water.

The liquid surface will be below the marking of 1.

In liquids of lower density.

When a hydrometer is dipped in a liquid of greater density, the liquid surface will be below the marking of 1. But in a liquid of lower density, the hydrometer sinks more and the liquid surface will be above the marking of 1. Relative density of water is 1, and that of liquids with higher density will be greater than 1 and that of liquids with lower density will be less than 1.

Following example to understand operator precedence available in Python programming language :

#!/usr/bin/python

a = 20

 b = 10 

c = 15 

d = 5 

e = 0 

e = (a + b)*c/d #(30*15)/5 

print “Value of (a + b) * c / d is “, e

e = ((a + b) * c)/d #(30*15)/5 

print “Value of ((a + b) * c) / d is “, e

e = (a + b) * (c / d); # (30) * (15/5) 

print “Value of (a + b) * (c / d) is “, e

e = a + (b*c)/d; # 20 + (150/5) 

print “Value of a + (b * c) / d is “, e

When you execute the above program it produces following result:

Value of (a + b) * c / d is 90 

Value of ((a + b) * c) / d is 90 

Value of (a + b) * (c / d) is 90 

Value of a + (b * c) / d is 50

i. (d) a generator

ii. (a) increases

iii. (a) the right hand thumb rule

iv. (a) 1000 J

v. (a) 99 W

(4) The magnetic lines of force are in concentric circles with the wire as the centre, in a plane perpendicular to the conductor.

In the parallel arrangement of electric appliances, the applied potential difference is the same in each case. Further, even if one of the appliances does not work or is removed for repairing, the other appliances can still be used.

(1) If an electric device rated 230 V, 5 A is operated for one hour, electric energy used

= VIt = 230 V × 5 A × 3600 s = 4140000 joules.

(2) If this energy is expressed in kW.h, it will be \(\frac{4140000}{3.6\times10^6}\) kW·h = 1.15 kW·h (more convenient). 3.6 × 10⁶

Hence, in practice the unit kW·h is used for the measurement of electric energy, rather than the joule.

(D) All the above

If a bare live wire (phase wire) and a bare neutral wire touch each other (come in direct contact) or come very close to each other, the resistance of the circuit becomes very small and hence huge (very high) electric current flows through it. This condition is called a short circuit or short circuiting.

In this case, a large amount of heat is produced and the temperature of the components involved becomes very high. Hence, the circuit catches fire.

(D) All the above

Yes, I do think so. 

e.g :

1. There are learned teachers in our school. 

2. We have all the needed facilities. 

3. Lessons are taught in Labs and LCD room. 

4. We enjoy freedom with responsibility. 

5. Our teachers are the architects of our future.

i. A) East Indies

ii. B) West Indies

iii. B) Spain

iv. B) Amerigo Vespucci

v. A) Italian

Answer is (A) Clergies

Answer is (C) Ginning

B) Leonardo da Vinci

Relationship between density and pressure: With increase in pressure, gas molecules get closer and the density (d) of the gas increases. Hence, at constant temperature, pressure is directly proportional to the density of a fixed mass of gas.

From Boyle’s law,

PV = k₁ …….(1)

∴ V = \(\frac{k_1}P\)

But, d = \(\frac{m}V\)

On substituting, V from equation (2),

d = \(\frac{m}{k_1}\) x P

∴ d = k P …….(3) 

where k = New constant 

∴ d ∝ P

Above equation shows that at constant temperature, the pressure is directly proportional to the density of a fixed mass of the gas.

The lowest hypothetical or imaginary temperature at which gases are supposed to occupy zero volume is called absolute zero.

Five elements and five compounds that exist as gases at room temperature are as follows :

• Air is a mixture of various gases.
• One cannot see air but can feel the cool breeze.
• The composition of air by volume is around 78 percent N₂, 21 percent O₂ and 1 percent other gases including CO₂. 

(i) Evaporation occurs at the surface of the liquid whereas boiling occurs at the entire liquid.

(ii) Evaporation occurs at any temperature whereas boiling occurs at a specific temperature.

Boyle‟s law states that “at constant temperature, the pressure of affixed amount of gas is inversely proportional to its volume”.

Mathematically, Pα 1/V at constant T or P = k/V

(b) Four times

Ideal gas law is a law relating the pressure, temperature and volume of an ideal gas.
Ideal gas equation is combination of three laws (Boyle’s Law, Charles’ Law and Avogadro Law) and gives a single equation (PV = nRT) called as Ideal gas equation.
Mathematically,
According to Boyle’s law; at constant T and n,
V ∝ 1/P …(1)
According to Charle’s law; at constant P and n,
V ∝ T …(2)
According to Avogadro law; at constant T and n,
V ∝ n …(3)
From equation 1, 2 and 3; we get,
V ∝ nT/P …(4)
Or, V = RnT/P …(5)
or, PV = nRT …(6)
Then, R = PV/nT …(7)
Where, R is a gas constant which is same for all gases and known as Universal gas constant and equation (6), PV = nRT is known as ideal gas equation.

A reagent that takes away electron pair is called electrophile. 

i.e.electron seeking e.g., > C= O , R₃C – X 

(d) lit atm K^-1 mole^-1

(b) 0°C, 4.7 atm

The atmospheric pressure is less and so boiling point is lowered.

T₁ = 15+273 = 288K , V₁ = 3L

T₂ = -73 + 273 = 200 K , V₂ = ?

V₁/T₁ = V₂ / T₂ , V₂ 

= ( 3 x 200) /288 

= 2.08 L.

(a) In the molecules HCl, HBr and HI, dipole-dipole interaction and London forces are present. 

(b) Dipole moment of HCl > HBr > HI but boiling point of HCl < HBr <HI.It means London forces are predominant over dipole-dipole interaction which depends upon surface area.HCl has least surface area, Whereas HI has maximum surface area. 

(c) HF has highest dipole moment due to highest difference in electronegativity, therefore hydrogen bonding is also present due to which force of attraction will increase, hence it has higher boiling point. 

The causes of deviations from ideal behaviour may be due to the following two assumptions of kinetic theory of gases:

The volume occupied by gas molecules is negligibly small as compared to the volume occupied by the gas. The forces of attraction between gas molecules are negligible.

This is valid only at low pressure and high temperature, when the volume occupied by the gas molecules is negligible as compared to the total volume of the gas. Two conditions in which ideal gases show deviation:

1. At low temperature or

2. At high pressure

The volumes of molecules are no more negligible as compared to the total volume of the gas and the gas molecules interact with each other due to proximity.

Kr has higher boiling point because it has a higher molecular weight (84 amu vs 40 amu). Consider the size pf the atoms and the interatomic forces (since the noble gases exist as single atoms) involved. The only forces are van der Waal’s (or London Dispersion) forces. These are a function of the polarizability of the atom, which is determined by diffusion of the electron cloud. The size of the atoms increases as we go down the group in Periodic table. It also increases as number of electrons increases. Hence, the electron cloud gets bigger, and the polarizability also increases. The electrons can move around easily so there will be instantaneous dipole moments (one side will be + and the other side will be -) which will also result in greater van der Waal’s/London Dispersion forces. Therefore, Kr has higher boiling point than Argon.

Mixture of NH₃ and HCl gases do not follow Dalton’s law of partial pressure because the gases are reactive. They react to form ammonium chloride which is solid and Dalton’s law of partial pressure is not applicable to solids and reactive gases.
NH₃ + HCl ➝ NH₄Cl

i) Evaporation occurs at all temperatures while boiling occurs at boiling point. 

ii) Evaporation is surface phenomenon while boiling occurs throughout the bulk of liquid. 

iii) Evaporation is slow while boiling is rapid. 

The number of unpaired electrons in the B₂ molecule is 2.

Bond order (b.o.) is defined as one half the difference between the number of electrons present in the bonding and the antibonding orbitals i.e., Bond order (b.o.) = ½ (Nb–Na) 

Bond order is inversely proportional to bond length

Cu is largest due to less effective nuclear charge. It has 29 electrons, 29 protons, Cu⁺ has 28 electrons and 29 protons, Cu²⁺ has 27 electrons and 29 protons.

The force of friction which one part of the liquid offers to another part of the liquid is called viscosity. Its unit is poise.

(i) Both lithium and magnesium react slowly with water. Their oxides and hydroxides are less soluble in water. 

(ii) Both are harder and lighter than other elements in the group.

The force acting parallel to the surface and perpendicular to a line of unit length anywhere in the surface is called surface tension. Its unit is Nm^-1 .

Metallic character. Lower the ionization energy more will be the tendency to lose electron, higher will be the metallic character. 

Gases can be liquefied by decrease of temperature and increase of pressure.

i) viscosity. Its unit is poise. 

 ii) surface tension. Its unit is Nm^-1 . 

In addition to horizontal and vertical trends in a periodic table; there is a diagonal relationship between certain sets of elements (Li and Mg, Be and Al, B and Si) that have upper left/lower right relative location in the periodic table. These pairs of elements share similar size and electronegativity, resulting in similar properties. Diagonal relationship is due to the increase in the charge in the ion and decrease in the size of ion as we move along the period.

Penetration effect. Due to a shape of the orbital,selectron penetrates nearer to the nucleus than p, d or f-electrons and are more tightly held.

 Both decrease by increasing temperature.