Reaction of calcium with water
Calcium reacts slowly with water. This is in contrast with magnesium, immediately above calcium in the periodic table, which is virtually unreactive with cold water. The reaction forms calcium hydroxide, Ca(OH)2 and hydrogen gas (H2).
In the case of the liquid meniscus, a concave meniscus that is what one usually observes takes place when the molecules of the liquid are fascinated towards the container. This takes place with water and a glass tube. A convex meniscus takes place when the molecules exhibit a stronger attraction with each other in comparison to the container, as in the case of glass and mercury.
The shape of the liquid meniscus is determined by the relative magnitudes of the cohesive forces in the liquid and adhesive forces between the liquid and its container.
Answer : The number of moles of 
produced will be, 0.241 moles.
Solution : Given,
Mass of Fe = 27.0 g
Molar mass of 
= 56 g/mole
First we have to calculate the moles of .
Now we have to calculate the moles of
The balanced chemical reaction is,
From the reaction, we conclude that
As, 4 mole of react to give 2 mole of
So, 0.482 moles of react to give 
moles of
Thus, the number of moles of produced will be, 0.241 moles.
Answer:
The change in entropy is -1083.112 joules per kilogram-Kelvin.
Explanation:
If the water is cooled reversibly with no phase changes, then there is no entropy generation during the entire process. By the Second Law of Thermodynamics, we represent the change of entropy (
), in joules per gram-Kelvin, by the following model:
(1)
Where:
- Mass, in kilograms.
- Specific heat of water, in joules per kilogram-Kelvin.
, 
- Initial and final temperatures of water, in Kelvin.
If we know that 
, 
, 
and 
, then the change in entropy for the entire process is:
The change in entropy is -1083.112 joules per kilogram-Kelvin.
