I believe it is D. Hope this helps you!
Answer:
6.2 g
Explanation:
In a first-order decay, the formula for the amount remaining after <em>n</em> half-lives is
where
<em>N</em>₀ and <em>N</em> are the initial and final amounts of the substance
1. Calculate the <em>number of half-lives</em>.
If
2. Calculate the <em>final mass</em> of the substance.
Ca(s)+2Hcl(aq) ------>CaCl2(s)+H2(g)
Explanation:
As per the Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
Hence, according to this law the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
..........(1)
..............(2)
The final reaction is as follows:
.............(3)
Therefore, adding (1) and (2) we get the final equation (3) and value of
at 298 K will be as follows.
=
+
= -314 kJ + (-80) kJ
= -394 kJ
Thus, we can conclude that
at 298 K for the given process is -394 kJ.
The correct answer is B. Platinum is the transition element among the choices. The elements belonging to this group are those having a partially filled d or f subshell. It usually refers to the d-block transition elements of the periodic table.