The graph shows the boiling points of the hydrogen compounds of Group 16 elements. Which statement correctly explains why water does not fit the trend of the other compounds?
A.
There are fewer electrons in the oxygen atoms so there is less shielding of the nuclear charge.
B.
There are strong hydrogen bonds in water but not in the other compounds.
C.
The covalent bonds in water are much stronger than in the other compounds.
D.
The water molecules are smaller and so have stronger van der Waals' forces.
Exam No:9701_s24_qp_11 Year:2024 Question No:8
Answer:
B
Knowledge points:
3.6.1.1 describe hydrogen bonding, limited to molecules containing N–H and O–H groups, including ammonia and water as simple examples
3.6.1.2.1 its relatively high melting and boiling points
3.6.1.2.2 its relatively high surface tension
3.6.1.2.3 the density of the solid ice compared with the liquid water
3.6.2 use the concept of electronegativity to explain bond polarity and dipole moments of molecules
3.6.3.1 describe van der Waals’ forces as the intermolecular forces between molecular entities other than those due to bond formation, and use the term van der Waals’ forces as a generic term to describe all intermolecular forces
3.6.3.2.1 instantaneous dipole – induced dipole (id-id) force, also called London dispersion forces
3.6.3.2.2 permanent dipole – permanent dipole (pd-pd) force, including hydrogen bonding
3.6.3.2.3 tdescribe hydrogen bonding and understand that hydrogen bonding is a special case of permanent dipole – permanent dipole force between molecules where hydrogen is bonded to a highly electronegative atom
3.6.3.3 describe hydrogen bonding and understand that hydrogen bonding is a special case of permanent dipole – permanent dipole force between molecules where hydrogen is bonded to a highly electronegative atom
3.6.4 stae that, in general, ionic, covalent and metallic bonding are stronger than intermolecular forces
Solution:
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