Practice Pakistan questions with answers and explanations.
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Water has polar O-H bonds and a bent shape.
The bond dipoles do not cancel.
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Low pressure keeps particles far apart.
High temperature reduces the relative importance of attractions.
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Oxygen has two bonding pairs and two lone pairs.
Lone-pair repulsion produces a bent molecule.
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Carbon has two electron domains from the two double bonds.
They arrange 180 degrees apart.
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Boron has three bonding regions and no lone pairs.
The molecule is planar with approximately 120-degree angles.
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Four equivalent bonding directions correspond to sp3 hybridization.
The ideal geometry is tetrahedral.
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Helicase breaks hydrogen bonds between base pairs.
It opens the replication fork.
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Three electron groups arrange about 120 degrees apart.
They lie in one plane.
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Four electron groups point toward tetrahedral corners.
The ideal bond angle is about 109.5 degrees.
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Carbon in methane has four bonding pairs and no lone pairs.
The molecular geometry is tetrahedral.
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Nitrogen has three bonds and one lone pair.
The lone pair changes the molecular shape from tetrahedral electron geometry.
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DNA contains the five-carbon sugar deoxyribose.
RNA contains ribose instead.
