Answer:
Explanation:
The total energy or intrinsic energy of a system is called the enthalpy. In thermochemistry, we have two types of enthalpy changes which are:
- Exothermic changes
- Endothermic changes
For the freezing of water, the enthalpy change is an exothermic one. Exothermic changes are designated as negative. In this chemical change, heat is liberated to the surroundings and this leaves the environment at a much higher temperature. In freezing, the enviroment gains more heat as the material begins to cool to lower temperature.
Entropy is the degree of randomness or disorderliness of a system. When a phase change occurs from liquid to solid, freezing takes place. Such a change increases the orderliness of a system and entropy diminishes. Here, entropy is negative.
The free energy is a measure of the energy a system that does useful work. Free energy depends on enthalpy, entropy and temperature of a system. For phase changes such as freezing of water, the value of free energy change is 0.
For this process, an increases in temperature makes it non-spontaneous. Increasing temperature would alter the course of the reaction and makes it exothermic. For entropy, increasing temperature would increase entropy and therefore, the reaction would not be feasible.
Temperature would mostly affect the free energy. An increase in temperature would increase the value of entropy change and the reaction would not be spontaneous. With falling temperature value, the reaction becomes more spontaneous and favored.
Answer:
When hydrogen is subjected to large enough pressure, it solidifies according to theory.
Explanation:
According to theory, when hydrogen molecules are subjected to enormous degree of pressure the molecules will solidify.
What happens here is that the hydrogen–hydrogen bonds in the hydrogen molecule will break apart and the molecules collapses into hydrogen atoms.
Hence, when hydrogen is subjected to large enough pressure, it solidifies according to theory.
Answer:
Directly
Explanation:
If V increases, then T must also increase to keep the same ratio.
If V decreases, then T must also decrease to keep the same ratio.
V and T are directly proportional, because a change in one always causes a change in the other and the changes are in the same ratio. The constant k is called the proportionality constant.
Answer:
H20
Explanation:
H20, is water and this is an example of a molecule. Molecules are "atoms bonded together." And hydrogen and oxygen are bonded making it a molecule.
Answer: 72 grams of 
are needed to completely burn 19.7 g 
Explanation:
According to avogadro's law, 1 mole of every substance weighs equal to molecular mass and contains avogadro's number 
of particles.
To calculate the number of moles, we use the equation:
Putting in the values we get:
According to stoichiometry:
1 mole of 
requires 5 moles of oxygen
0.45 moles of require= 
moles of oxygen
Mass of 
72 grams of are needed to completely burn 19.7 g
