The book<span> documented the detrimental effects on the environment—particularly on birds—of the indiscriminate use of pesticides. -A</span>
Explanation:
A chemical reaction equation that contains same number of atoms on both reactant and product side is known as a balanced chemical reaction equation.
For example, 
Here, number of reactant molecules are as follows.
Na = 2
S = 2
Cd = 1
O = 4
Number of product molecules are as follows.
Na = 2
S = 2
Cd = 1
O = 4
As there are already equal number of atoms on both reactant and product side. Hence, the reaction equation is balanced.
Also, in this reaction both 
and 
are present as aqueous solution. And, CdS is the precipitate that is formed as it is the insoluble solid that forms.
is present in aqueous state.
Answer:
- <em>The mystery substance is</em> <u>C. Bromine (Br) </u>
Explanation:
<em>Argon (Ar) </em>is a noble gas. Whose freezing point is -189 °C (very low), thus it cannot be the frozen substance. Also, it is not reactive, thus is would have not reacted with iron. Hence, argon is not the mystery substance.
<em>Scandium (Sc) </em>is a metal from group 3 of the periodic table, thus is will not react with iron. Thus, scandium is not the mystery substance.
Both <em>bromine</em> and <em>iodine</em> are halogens (group 17 of the periodic table).
The freezing point of bromine is −7.2 °C, and the freezing point of iodine is 113.7 °C. Thus, both could be solids (frozen) in the lab.
The reactivity of the halogens decrease from top to bottom inside the group. Bromine is above iodine. Then bromine is more reactive than iodine.
Bromine is reactive enough to react with iron. Iodine is not reactive enough to react with iron.
You can find in the internet that bromine vapour over hot iron reacts producing iron(III) bromide. Also, that bromine vapors are red-brown.
Therefore, <em>the mystery substance is bromine (Br).</em>
I did the math and i got 450 but i dont know if its right
