Heat; rather, or change of the molecules to make them move faster
Answer:a. 1-propanol,
Explanation:
Boiling point depends on the relative molecular mass of the compound and the kind of intermolecular interactions present in the substance. 1-propanol has a relative molecular mass of 60 and posses strong intermolecular hydrogen bonding. The presence of hydrogen bonding is known to lead to an increase in boiling point. As a result of this, it is obvious that 1-propanol has the highest boiling point among other compounds in the list.
Ans: B) semiconductor
Photovoltaic cells work by converting light energy to electrical energy. These cells are essentially made of silicon based semiconductors. When photons (light energy) strike the surface of the semiconducting material electrons are let loose. The delocalization of electron creates a flow of charge which produces electricity.
Thus, it is the semiconductor present in a photovoltaic cell which is responsible for converting light to electricity.
Answer:
(a) Condensation:Exothermic
(b) Sublimation: Endothermic
(c) Vaporization: Endothermic
(d) Freezing: Exothermic
Explanation:
When a phase change occurs, for example going from a liquid to a gas we need to increase the kinetic energy of the molecules to escape to the gas phase where the kinetic energy of the molecules is greater. By the contrary if we remove energy we slow down the molecules increasing their atttraction and slowing them as it occurs when the goes into the liquid state, hence this phase change is exothermic.
(a) Condensation : when the phase change is from a gas by definition we have a condensation phase chanhe. The reaction is exothermic, we need to cool the gas to condense.
(b) Sublimation: crystals of iodine disappear from an evaporating dish as they stand in a fume hood : this phase change receives the name of sublimation and it occurs when a solid goes directly to the gas phase without going through the liquid phase. We need to increase the energy of the molecules so it can go to the gas phase and the change is endothermic.
(c) Vaporization : rubbing alcohol in an open container slowly disappears: this phase change is vaporization and by difinition is when the liquid goes to the gas phase, hence its name vaporization. The change is endothermic, we need heat from the sorroundings to give the molecules of the liquid enough energy to escape into the vapor phase.
(d) Molten lava from a volcano turns into solid rock : this phase change is freezing and we need to lower the energy of the liquid by releasing it to the sorroundings, therore it is an exothermic phase change.
You need the solubility of the LiCl in water at 20°C.
The solubilities are shown in tables. Many books contain those tables. You have to make sure that the solubility is shown in the same solvent and at the same temperature that you are going to prepare the solution.
In this case the solubility of LiCl in water at 20°C is 83.05 g of LiCl in 100 g of H2O. Check if your book and your teacher work with the same value.
Using 8.05 g LiCl / 100 g of water you get:
300 g of water * 83.05 g LiCl / 100 g of water = 249.15 g of LiCl.
Answer: 249.15 g of LiCl
