Class 11 - Chemistry
Assertion (A): Liquids tend to have maximum number of molecules at their surface.
Reason (R): Small liquid drops have spherical shape.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(d) Liquid tends to acquire minimum surface area due to surface tension. Thus, small liquid drops are spherical. In spherical shape, surface area is minimum.
Questions and Answers
2.9 g of a gas at 95 °C occupied the same volume as 0.184 g of hydrogen at 17 °C at the same pressure. What is the molar mass of the gas ?
A mixture of dihydrogen and dioxygen at one bar pressure contains 20% by weight of dihydrogen. Calculate the partial pressure of dihydrogen.
What would be the SI unit for the quantity PV2T2/n?
In terms of Charles’ law explain why -273 °C is the lowest possible temperature.
Explain the physical significance of vander Waals parameters.
What is the value of the gas constant in SI units?
Define boiling point of a liquid.
What is SI unit of (i) Viscosity (ii) Surface tension?
What is the effect of temperature on (i) surface tension and (ii) Viscosity?
What is the unit of coefficient of viscosity?
What do you understand by laminar flow of a liquid?
What do you mean by compressibility factor?
What is Boyle Temperature?
Define an ideal gas.
Name four properties of gases.
State Dalton's law of partial pressure.
What do you mean by aqueous tension?
Give mathematical expression for ideal gas equation.
Write van der Waals equation for n moles of a gas.
How is compressibility factor expressed in terms of molar volume of the real gas and that of the ideal gas?
Why liquids diffuse slowly as compared to gases?
What is the effect of temperatures on the vapour pressure of a liquid?
Why falling liquid drops are spherical?
A weather balloon has a volume of 175 dm3 when filled with hydrogen gas at a pressure of 1.0 bar. Calculate the volume of the balloon when it rises to a height where the atmospheric pressure is 0.8 bar. Assume that temperature is constant.
A certain amount of a gas at 27 °C and 1 bar pressure occupies a volume of 25 m3. If the pressure is kept constant and the temperature is raised to 77 °C, what will be the volume of the gas?
A flask was heated from 27 °C to 227 °C at constant pressure. Calculate the volume of the flask if 0.1 dm3 of air measured at 227 °C was expelled from the flask.
At 25 °C and 760 mm ofHg pressure a gas occupies 600 mL volume. What will be its pressure at a height where temperature is 10 °C and volume of the gas is 640 mL?
A 34.0 dm3 cylinder contains 212 g of oxygen gas at 21 °C. What mass of oxygen must be released to reduce the pressure in the cylinder to 1.24 bar?
The values of the van der Waal’s constants for a gas are a = 4.10 dm6 bar mol-2 and b = 0.035 dm3 bar mol-1. Calculate the values of the critical temperature and critical pressure for the gas.
The pressure of a mixture of H2 and N2 in a container is 1200 torr. The partial pressure of nitrogen in the mixture is 300 torr. What is the ratio of H2 and N2 molecules in the mixture?
(a) What do you mean by’Surface Tension'of a liquid?
(b) Explain the factors which can affect the surface tension of a liquid.
A neon-dioxygen mixture contains 70.6 g dioxygen and 167.5g neon. If pressure of the mixture of gases in the cylinder is 25 bar. What is the partial pressure of dioxygen and neon in the mixture?
State and explain Boyle’s law. Represent the law graphically.
Give an expression for the van der Wools equation. Give the significance of the constants used in the equation. What are their units?
What are ideal and real gases? Out of CO2 and NH3 gases, which is expected to show more deviation from the ideal gas behaviour?
State and explain Dalton’s law of partial pressures. Can we apply Dalton's law of partial pressures to a mixture of carbon monoxide and oxygen?
(a) Why aerated water bottles kept under water during summer?
(b) Which property of liquid is responsible for spherical shape of drop?
(c) Why is moist air lighter than dry air?
(d) Define aqueous tension.
(e) What are units of a and b which are van der Waals constants?
Why does sharpened edge becomes smooth on heating up to melting point?
Arrange the following in order of increasing density:
An O2 cylinder has 10 LO2 at 200 atm. If patient takes 0.50 ml of O2 at 1 atm in one breath 37 °C, how many breaths are possible?
What is SI unit of viscosity coefficient (Î·)?
(b) N s m-2
(c) km -2 s
(d) N m-2
With regard to the gaseous state of matter which of the following statements are correct?
(a) Complete order of molecules (b) Complete disorder of molecules
(c) Random motion of molecules (d) Fixed position of molecules
Which of the following figures does not represent 1 mole of dioxygen gas at STP?
(a) 16 grams of gas
(b) 22.7 litres of gas
(c) 6.022 x 1023 dioxygen molecules
(d) 11.2 litres of gas
Under which of the following two conditions applied together, a gas deviates most from the ideal behaviour?
(a) Low pressure (b) High pressure
(c) Low temperature (d) High temperature
Which of the following changes decrease the vapour pressure of water kept in a sealed vessel?
(a) Decreasing the quantity of water
(b) Adding salt to water
(c) Decreasing the volume of the vessel to one-half
(d) Decreasing the temperature of water
If 1 gram of each of the following gases are taken at STP, which of the gases will occupy (a) greatest volume and (b) smallest volume? CO, H20, CH4, NO
Physical properties of ice, water and steam are very different. What is the chemical composition of water in all the three states?
The behaviour of matter in different states is governed by various physical laws. According to you what are the factors that determine the state of matter?
Use the information and data given below to answer the questions (a) to (c):
• Stronger intermolecular forces result in higher boiling point.
• Strength of London forces increases with the number of electrons in the molecule.
• Boiling point of HF, HC1, HBr and HI are 293 K, 189 K, 206 K and 238 K respectively.
(a) Which type of intermolecular forces are present in the molecules HF, HC1, HBr and HI?
(b) Looking at the trend of boiling points of HC1, HBr and HI, explain out of dipole-dipole interaction and London interaction, which one is predominant here?
(c) Why is boiling point of hydrogen fluoride highest while that of hydrogen chloride lowest?
What will be the molar volume of nitrogen and argon at 273.15 K and 1 atm?