Answer: A. Liquefy hydrogen under pressure and store it much as we do with liquefied natural gas today.
Explanation:
Current Hydrogen storage methods fall into one of two technologies;
- <em>physical storage</em> where compressed hydrogen gas is stored under pressure or as a liquid; and
- <em>chemical storage</em>, where the hydrogen is bonded with another material to form a hydride and released through a chemical reaction.
Physical storage solutions are commonly used technologies but are problematic when looking at using hydrogen to fuel vehicles. Compressed hydrogen gas needs to be stored under high pressure and requires large and heavy tanks. Also, liquid hydrogen boils at -253°C (-423°F) so it needs to be stored cryogenically with heavy insulation and actually contains less hydrogen compared with the same volume of gasoline.
Chemical storage methods allow hydrogen to be stored at much lower pressures and offer high storage performance due to the strong binding of hydrogen and the high storage densities. They also occupy relatively smaller spaces than either compressed hydrogen gas or liquified hydrogen. A large number of chemical storage systems are under investigation, which involve hydrolysis reactions, hydrogenation/dehydrogenation reactions, ammonia borane and other boron hydrides, ammonia, and alane etc.
Other practical storage methods being researched that focuses on storing hydrogen as a lightweight, compact energy carrier for mobile applications include;
- Nanostructured metal hydrides
- Liquid organic hydrogen carriers (LOHC)
Answer:
The mass percentage of calcium carbonated reacted is 2.5%.
Explanation:
The reaction is:
Thus the Kp of the equilibrium will be:
Kp = partial pressure of carbon dioxide [as the other are solid]
Moles of calcium carbonate initially present = 
Let us apply ICE table to the equilibrium given:
Initial 0.2 0 0
Change -x +x +x
Equilibrium 0.2-x x x
Kp = partial pressure of carbon dioxide
Kp = Kc(RT)ⁿ
where n = difference in the number of moles of gaseous products and reactants
for given reaction n = 1
R = gas constant = 8.314 J /mol K
T = temperature = 800 ⁰C = 1073 K
Putting values
Kc =
Kc = ![\frac{[CO_{2}][CaO]}{[CaCO_{3}]}= \frac{x^{2} }{(0.2-x)}=1.3X10^{-4}](https://tex.z-dn.net/?f=%5Cfrac%7B%5BCO_%7B2%7D%5D%5BCaO%5D%7D%7B%5BCaCO_%7B3%7D%5D%7D%3D%20%5Cfrac%7Bx%5E%7B2%7D%20%7D%7B%280.2-x%29%7D%3D1.3X10%5E%7B-4%7D)
On calculating
x = 0.005
where x = the moles of calcium carbonate dissociated or reacted.
Percentage of the moles or mass reacted = 
%
Answer:
8.09x10⁻⁵M of Fe³⁺
Explanation:
Using Lambert-Beer law, the absorbance of a sample is proportional to its concentration.
In the problem, the Fe³⁺ is reacting with KSCN to produce Fe(SCN)₃ -The red complex-
The concentration of Fe³⁺ in the reference sample is:
4.80x10⁻⁴M Fe³⁺ × (5.0mL / 50.0mL) = 4.80x10⁻⁵M Fe³⁺
<em>Because reference sample was diluted from 5.0mL to 50.0mL.</em>
<em>That means a solution of 4.80x10⁻⁵M Fe³⁺ gives an absorbance of 0.512</em>
Now, as the sample of the lake gives an absorbance of 0.345, its concentration is:
0.345 × (4.80x10⁻⁵M Fe³⁺ / 0.512) = <em>3.23x10⁻⁵M. </em>
As the solution was diluted from 20.0mL to 50.0mL, the concentration of Fe³⁺ in Jordan lake is:
3.23x10⁻⁵M Fe³⁺ × (50.0mL / 20.0mL) = <em>8.09x10⁻⁵M of Fe³⁺</em>
Answer:
44 g
Explanation:
The formula for the number of moles (n) is equal to 
.
Since we need to find the mass, we derive it from the formula of the number of moles and we get that mass = n x molecular weight .
The molecular weight of 
= 12 g/mol (from the carbon) + 19x4 g/mol (from the 4 fluorine atoms)= 88 g/mol
We plug in the numbers in the derived formula for the mass and we get :
mass = n x molecular weight = 0.5 mol x 88 g/mol = 44 g
