Bonding, shapes and forces

0 of 10 answered, 0 correct

1. Question 1 of 10

   Potassium bromide conducts electricity when molten but not when solid. Why?

   AA, In the solid the electrons are held in fixed positions; when molten the electrons are free to move.BB, In the solid the ions are held in fixed positions; when molten the ions are free to move.CC, The solid contains no ions; melting breaks covalent bonds to form ions.DD, In the solid the molecules are held in fixed positions; when molten the molecules are free to move.

2. Question 2 of 10

   Ammonia reacts with boron trifluoride to form H₃NBF₃. How is the bond between nitrogen and boron formed?

   AA, The nitrogen atom donates a lone pair to the boron atom.BB, The boron atom donates a lone pair to the nitrogen atom.CC, The nitrogen and boron atoms each give one electron to the bond.DD, The nitrogen atom transfers one electron to the boron atom.

3. Question 3 of 10

   Which is the definition of electronegativity?

   AA, The energy needed to remove one electron from an atom.BB, The ability of an atom to gain an electron and form a negative ion.CC, The ability of an atom to attract the pair of electrons in a covalent bond.DD, The ability of a molecule to attract electrons from a neighbouring molecule.

4. Question 4 of 10

   Which molecule has a permanent dipole?

   AA, CO₂BB, BCl₃CC, SiCl₄DD, PF₃

5. Question 5 of 10

   What is the shape of the H₃O⁺ ion?

   AA, Trigonal planarBB, PyramidalCC, TetrahedralDD, Bent

6. Question 6 of 10

   Why is the H–O–H bond angle in water smaller than the H–N–H bond angle in ammonia?

   AA, Oxygen is more electronegative than nitrogen, so its bonds are pulled closer together.BB, Water has only two bonding pairs, which repel each other less than three do.CC, Water has two lone pairs, and lone pairs repel more strongly than bonding pairs.DD, Hydrogen bonds between water molecules pull the hydrogen atoms closer together.

7. Question 7 of 10

   What is the H–C=O bond angle in propanal?

   AA, 90°BB, 104.5°CC, 109.5°DD, 120°

8. Question 8 of 10

   Which of these substances has hydrogen bonding between its molecules?

   AA, CH₃NH₂BB, CH₃OCH₃CC, CH₃CHODD, HCl

9. Question 9 of 10

   Bromine, Br₂, boils at 59 °C but hydrogen bromide, HBr, boils at −66 °C. Why does bromine boil at the higher temperature?

   AA, The Br–Br covalent bond is stronger than the H–Br covalent bond.BB, Br₂ has many more electrons, so its van der Waals forces are stronger.CC, Br₂ molecules have a larger permanent dipole than HBr molecules.DD, HBr molecules are non-polar, so there are few forces between them.

10. Question 10 of 10

    Why does calcium melt at a higher temperature than potassium?

    AA, Calcium atoms share more electrons, forming stronger covalent bonds.BB, Calcium atoms have stronger van der Waals forces between them.CC, Calcium ions have a higher charge and attract the delocalised electrons more strongly.DD, Calcium ions are larger, so they pack more closely together in the lattice.