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.
Let the volume of the flask = V dm3 (after expelling the air)
V1 = V dm3, T1 = 27 + 273 = 300K
VT2 = (V + 0.1) dm3, T2 = 227 + 273 = 500 K
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
Assertion (A): Gases do not liquefy above their critical temperature, even on applying high pressure.
Reason (R): Above critical temperature, the molecular speed is high and intermolecular attractions cannot hold the molecules together because they escape because of high speed.
(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.
Why does the boundary between liquid phase and gaseous phase disappear on heating a liquid up to critical temperature in a closed vessel? In this situation what will be the state of the substance?
One of the assumptions of kinetic theory of gases states that "there is no force of attraction between the molecules of a gas."How far is this statement correct? Is it possible to liquefy an ideal gas? Explain.
The critical temperature (Tc) and critical pressure (Pc) of C02 are 30.98 °C and 73 atm respectively. Can C02(g) be liquefied at 32 °C and 80 atm pressure?
Assertion (A): The temperature at which vapour pressure of a liquid is equal to the external pressure is called boiling temperature.
Reason (R): At high altitude atmospheric pressure is high.
(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.
Two different gases ˜A' and ˜9' are filled in separate containers of equal capacity under the same conditions of temperature and pressure. On increasing the pressure slightly, the gas ˜A' liquefies but gas ˜B' does not liquefy even on applying high pressure until it is cooled. Explain this phenomenon.
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
Assertion (A): Three states of matter are the result of balance between intermolecular forces and thermal energy of the molecules. .
Reason (R): Intermolecular forces tend to keep the molecules together but thermal energy of molecules tends to keep them apart.
(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.
(a) What do you mean by’Surface Tension'of a liquid?
(b) Explain the factors which can affect the surface tension of a liquid.
One of the assumptions of kinetic theory of gases is that there is no force of attraction between the molecules of a gas.
State and explain the evidence that shows that the assumption is not applicable for real gases.
At 0 °C, the density of a gaseous oxide at 2 bar is same as that of dinitrogen at 5 bar. What is the molecular mass of the oxide?
What will be the pressure of the gas mixture when 0.5 L of H2 at 0.8 bar and 2.0 L of dioxygen at 0.7 bar are introduced in all vessel at 27 °C?
A student forgot to add the reaction mixture to the round bottomed flask at 27 °C but instead, he/she placed the flask on the flame. After a lapse of time, he realized his mistake, and using a pyrometer, he found the temperature of the flask was 477 °C. What fraction of air would have been expelled out?
Calculate the temperature of 4.0 moles of a gas occupying 5 dm3 at 3.32 bar (R = 0.083 bar dm3 K-1 mol-1)
Critical temperature for Co2 and CH4 are 31.1 °C and -81.9 °C respectively. Which of these has stronger intermolecular forces and why ?
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?
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?
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
Density of a gas is found to be 5.46 g/dm3 at 27 °C and at 2 bar pressure. What will be its density at STP?
How much time would it take to distribute one Avogadro number of wheat grains if 1010 grains are distributed each second ?
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?
Compressibility factor, Z, of a gas is given as Z = PV/nRT
(i) What is the value of Z for an ideal gas?
(ii) For real gas what will be the effect on value of Z above Boyle's temperature?
Isotherms of carbon dioxide at various temperatures are represented in the following figure. Answer the following questions based on this figure.
(i) In which state will C02 exist between the points a and b at temperature T1
(ii) At what point will Co2 start liquefying when temperature is T1?
(iii) At what point will C02 be completely liquefied when temperature is T2?
(iv) Will condensation take place when the temperature is T3
(v) What portion of the isotherm at T1 represent liquid and gaseous C02 at equilibrium?
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) 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?
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?
Name the energy which arises due to motion of atoms or molecules in a body. How is this energy affected when the temperature is increased?
Viscosity of a liquid arises due to strong intermolecular forces existing between the molecules. Stronger the intermolecular forces, greater is the viscosity. Name the intermolecular forces existing in the following liquids and arrange them in the increasing order of their viscosities. Also give reason for the assigned order in one line.Water, Hexane (CH3CH2CH2CH2CH2CH3), Glycerine (CH2OHCH(OH)CH2OH)
Assertion (A): At constant temperature, PV vs V plot for real gases is not a straight line.
Reason (R): At high pressure all gases have Z> 1 but at intermediate pressure most gases have Z < 1.
(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.
Explain the term ‘laminar flow'. Is the velocity of molecules same in all the layers in laminar flow? Explain your answer.
A vessel of 120 mL capacity contains a certain amount of gas at 35 °C and 1.2 bar pressure. The gas is transferred to another vessel of volume 180 mL at 35 °C. What would be its pressure?
A mixture of dihydrogen and dioxygen at one bar pressure contains 20% by weight of dihydrogen. Calculate the partial pressure of dihydrogen.
How is compressibility factor expressed in terms of molar volume of the real gas and that of the ideal gas?
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?
