Calculate the amount (mass) of acetaldehyde (C2H40, molar mass = 44.0526 g mol-') that causes a
bomb calorimeter with a heat capacity of 12.91 kJ °C 1 to have a temperature increase from 27.8 °C
to 41.7 °C. The ALU for the combustion of acetaldehyde is -1166.9 kJ mol-1

Afraidsugar lol it’s the third one

Answerδh > 0explanationc₆h₆  (s)  → c₆h₆ (l)if you are changing it from a solid to a liquid, you are pretty much melting the solid. this requires heat energy. therefore, the reaction is endothermic (takes in energy); the system enthalpy increases as the reaction proceeds: δh > 0.

The mole ratio of hydrogen to ammonia is 3: 2.

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.