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Posted by MissChemTeacher_Bitesize (U15172316) on Sunday, 3rd February 2013
Try these questions on Polar and Non-Polar molecules, it'll give you a chance to look over Unit 1 stuff before your prelims.
1) Which of the following compounds has polar molecules?
2) When two atoms form a non-polar covalent bond, the two atoms must have:
A the same atomic size
B the same electronegativity
C the same ionisation energy
D the same number of outer electrons.
3) Some common molecules are shown. Each molecule contains at least one
polar covalent bond. Draw the shapes of each and decide, using symmetry, which of the following molecules is non-polar?
If you need help answering any of these questions get in touch.
Posted by MissChemTeacher_Bitesize (U15172316) on Monday, 18th February 2013
Solutions to the problems.
1) B - ammonia is a polar molecule. It has polar bonds between the hydrogen and nitrogen atoms and these polar bonds are arranged in a non-symmetrical manner making the molecule have an overall polar charge.
2) Atoms form non-polar covalent bonds when they have the same electronegativity value. For example, diatomic atoms are always non-polar as their electronegativity values are the same. Another example is a molecule of phosphorus hydride (phosphine) as the hydrogen and phosphorus atoms both have an electronegativity value of 2.2.
3) CO₂ is a molecule which contains polar bonds but due to its symmetry of these polar bonds it is an overall non-polar molecule.
If you need any more help with polar molecules and polar bonds feel free to get in touch.
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