Answer:
1.13 x 10²⁴formula units
Explanation:
Given parameters:
Number of moles of NH₄Cl = 1.87mol
Unknown:
Number of formula units = ?
Solution:
From mole concept;
1 mole of a substance contains 6.02 x 10²³ formula units
Now;
1.87 moles of NH₄Cl 1.87 x 6.02 x 10²³ = 1.13 x 10²⁴formula units
Answer: The value of ![[H_{3}O^{+}]](https://tex.z-dn.net/?f=%5BH_%7B3%7DO%5E%7B%2B%7D%5D)
is 0.0012 M and ![[OH^{-}]](https://tex.z-dn.net/?f=%5BOH%5E%7B-%7D%5D)
is 
.
Explanation:
pH is the negative logarithm of concentration of hydrogen ion.
It is given that pH is 2.89. So, the value of concentration of hydrogen ions is calculated as follows.
![pH = - log [H^{+}]\\2.89 = - log [H^{+}]\\conc. H^{+} = 0.0012 M](https://tex.z-dn.net/?f=pH%20%3D%20-%20log%20%5BH%5E%7B%2B%7D%5D%5C%5C2.89%20%3D%20-%20log%20%5BH%5E%7B%2B%7D%5D%5C%5Cconc.%20H%5E%7B%2B%7D%20%3D%200.0012%20M)
The relation between pH and pOH value is as follows.
pH + pOH = 14
0.0012 + pOH = 14
pOH = 14 - 0.0012 = 13.99
Now, pOH is the negative logarithm of concentration of hydroxide ions.
Hence, is calculated as follows.
![pOH = - log [OH^{-}]\\13.99 = - log [OH^{-}]\\conc. OH^{-} = 1.02 \times 10^{-14} M](https://tex.z-dn.net/?f=pOH%20%3D%20-%20log%20%5BOH%5E%7B-%7D%5D%5C%5C13.99%20%3D%20-%20log%20%5BOH%5E%7B-%7D%5D%5C%5Cconc.%20OH%5E%7B-%7D%20%3D%201.02%20%5Ctimes%2010%5E%7B-14%7D%20M)
Thus, we can conclude that the value of is 0.0012 M and is .
In an endothermic reaction, “delta H” is always positive, since the system is absorbing heat from its surroundings, not releasing into the surroundings like in an exothermic reaction where the delta H is always negative.
So our endothermic reactions would be the first (484kJ) and the last (92kJ).
