MgO + H2O à Mg(OH)2 is an example of a _________ chemical reaction. A. synthesis B. combustion C. replacement D. decomposition
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Answer: The correct option is The properties of a noble gas.
Explanation: There are 7 periods in the periodic table.
The last element of each period are Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn) and Ununoctium (Uuo).
- The electronic configuration for Helium is
. For He, The outermost electrons are 2.
- The electronic configuration for all the other elements is
( where, n = 2, 3, 4, 5, 6 and 7 respectively). For all the other gases, the outermost electrons are 8.
All these elements have stable electronic configuration and are not reactive in nature. Hence, they are considered as noble gases.
Therefore, the last element of each period always have the properties of a noble gas.
The molarity of formic acid is 100 mM or . The dissociation reaction of formic acid is as follows:
The expression for dissociation constant of the reaction will be:
Rearranging,
Here, pH of solution is 4.15 thus, concentration of hydrogen ion will be:
Similarly, thus,
Putting the values,
Therefore, the concentration of formate will be 0.2511 M.