Which among the following liquids is the best conductor of heat?
Correct Answer:
(A)
Mercury
Mercury is a chemical element with the symbol (Hg). Mercury is used in thermometers due to its special properties. It can measure a wide range of temperatures from -40 to 356oC and up to 570oC under pressure in a liquid state. It expands regularly in proportional to the absolute temperature changes. A heavy, silvery d-block element, mercury is the only common metal element which is found in liquid state at standard conditions for temperature and pressure. It is a metal, so it is a conductor of heat. Mercury is the poorest conductor of heat among all metals, but among the given options it is the best conductor of heat.
Ques:
52
The poorest conductor of heat among the following is :
Correct Answer:
(C)
Mercury
All metals are conductors of heat but lead and mercury are poor conductors of heat compared to other metals. Thermal conductivity of lead is about 34.7 w/mK while thermal conductivity of mercury is only about 8.31 w/mK. Hence, mercury is the poorest conductor of heat among all metals.
Ques:
53
Which one of the following metals is liquid at ordinary temperature?
Correct Answer:
(C)
Mercury
Mercury is the only common metal which is liquid at ordinary (room) temperature. Mercury is sometimes called quicksilver.
Ques:
54
Which of the following is in liquid form at room temperature?
Correct Answer:
(C)
Francium
There are two elements Bromine and Mercury that are liquid at the room temperature (298 K or 25oC). There are four more elements which melt just a few degree above room temperature. These are Francium, Caesium, Gallium and Rubidium.
Ques:
55
Water gas is
Correct Answer:
(A)
CO + H2
Water gas is a synthesis gas with the mixture of carbon monoxide (CO) and hydrogen (H2). Methyl alcohol is formed by water gas (CO + H2) –
CO + 2H2 → CH3OH (Catalyst process)
Ques:
56
The gas, which comes out on opening a soda water bottle, is :
Correct Answer:
(A)
Carbon dioxide
Soda water or carbonated water is water that has been infused with carbon dioxide gas under pressure. The gas, which comes out on opening a soda water bottle, is carbon dioxide that produces a bubbly drink.
Ques:
57
What is the bond order of CO group?
Correct Answer:
(D)
3
In Molecular orbital theory the bond order formula can be defined as half of the difference between the number of electrons in bonding orbitals and antibonding orbitals.
Bond order = 1/2 [Nb-Na]
Where,
Nb= number of bonding electrons
Na= number of antibonding electrons
CO (Carbon monoxide) molecule has 10 valence electrons, four from carbon atom (2s22p2) and six from oxygen atom (2s22p4). According to molecular orbital diagram, molecular orbital configuration is given as
Ꟙ2s2 Ꟙ*2s2 Ꟙ2pz2π2px2 π2py2
here, Nb = 8; Na = 2
Thus, Bond order of CO = 1/2[8 – 2] = 3
Note : Here the calculations are done ignoring the 1s orbitals because there will be 2 electrons in the bonding and 2 in the antibonding.
Ques:
58
Choose the incorrect pair:
Correct Answer:
(D)
Bleaching powder – Calcium oxide
Sodium carbonate is commonly known as Washing soda. Sodium Hydrogencarbonate is commonly known as Caustic soda. Ethanoic acid is commonly known as Acetic acid. calcium oxychloride is commonly known Bleaching powder.
Ques:
59
Dry ice is –
Correct Answer:
(C)
Solid CO2
Dry ice sometimes referred to as solid CO2 or dry snow is the solid (frozen) form of carbon dioxide.
Ques:
60
Which one of the following alloys is called an amalgam ?
Correct Answer:
(C)
Mercury - Zinc
An amalgam is a substance formed by the reaction of Mercury with another metal.