Atomic theory 10 Flashcards
Use electronegativity values to predict the type of bond expected between hydrogen and sulfur. (L.C)
Weakly polar / almost non-polar
Write the chemical equation for hydrogen sulphide. (L.C)
H₂S
Would you expect the hydrogen sulphide molecule to be linear or non-linear in shape? Justify your answer.(L.C)
- Non-linear
- There are lone(non-bonding) pairs
Hydrogen sulphide has a boiling point of 212.3 K and water has a boiling point of 373 K. Account for the difference in the boiling points of these substances. (L.C)
- Water has hydrogen bonds
- Weak dipole-dipole forces in H₂S /
- Weaker intermolecular forces in H₂S
Would you expect hydrogen sulphide to be soluble in water? Explain your answer. (L.C)
- No / only slightly soluble
- Does not form hydrogen with water
Explain the term intermolecular forces (L.C)
Attractive (repulsive) forces between molecules.
Use your knowledge of intermolecular forces to explain why methane has a very low boiling point (164°C) (L.C)
- Very weak intermolecular forces
- Weak Van der Waal’s forces of attraction
The relative molecular mass of methane is only slightly lower than that of water but the boiling point of water is much higher (100°C). Suggest a reason for this. (L.C)
- Much stronger hydrogen bonds between water molecules
Why do ionic substances conduct electricity when molten or dissolved in water but not in the solid state? (L.C)
Molten/dissolved : ions free to move
Solid : ions not free to move / ions locked in position
Show that the ammonia molecule (NH₃) has polar covalent bonding. Describe the processes involved when ammonia dissolves in water. (L.C)
- There is an electronegativity difference between N and H
- Showing unequal sharing
Define electronegativity (L.C)
The relative power of attraction an atom of an element has for the shared pair of electrons in a covalent bond.
Account for the difference in bond angle between the two molecules, 107.3 degrees in ammonia and 109.5 degrees in silane. (L.C)
- Lone pair of electrons has greater repelling power than a bond pair of electrons.
- Bonds in NH₃ pushed closer together than in SiH₄
- Ammonia has three bond pairs where silane has four bond pairs
Use electronegativity values to determine which bond, the N-H bond in ammonia or the Si-H bond in silane, is the more polar. (L.C)
N - H = 0.84
Si - H = 0.3
⇒
N - H is more polar
Define electronegativity (L.C)
The relative power of attraction an atom of an element has for the shared pair of electrons in a covalent bond.
Use electronegativity values to determine which bond, the N-H bond in ammonia or the Si-H bond in silane, is the more polar. (L.C)
N - H = 0.84
Si - H = 0.3
⇒ N - H is more polar
Which of the two substances ammonia (NH₃) or silane (SiH₄) has hydrogen bonding between its molecules? Justify your answer. (L.C)
- Ammonia
- In ammonia hydrogen bonded to a small highly electronegative element
Give the reason why a molecule with polar bonds can be non-polar. (L.C)
- Centres of positive and negative charge coincides
- Dipole moments cancel
Why is there an increase in electronegativity value moving from gallium to germanium in the periodic table? (L.C)
- Nuclear charge increasing
- Atomic radius increasing
Define electronegativity (L.C)
The relative power of attraction an atom of an element has for the shared pair of electrons in a covalent bond..
Write the molecular formula for the simplest compound formed between germanium (IV) and hydrogen. (L.C)
GeH₄
Would you expect the compound GeH₄ to be water soluble? Explain your answer. (L.C)
- No
- GeH₄ is a non-polar solute
Suggest a reason why ammonia has the highest boiling point of ammonia, phosphine and arsine. (L.C)
Hydrogen bonding in ammonia (azane) is stronger than the other intermolecular forces in phosphane or arsane.
Suggest a reason why phosphine’s boiling point is lower than that of arsine. (L.C)
- Phosphine molecules are smaller
- Phosphine has a smaller degree of intermolecular forces
Define electronegativity (L.C)
The relative power of attraction an atom of an element has for the shared pair of electrons in a covalent bond.
