I already answered this question in Spanish language. Now I answer in English.
Answer: the chemical changes.
Explanation:
We understand by composition of a substance to the proportion (ratio or percentage) of each element (type of atoms) that makes up the same, as well as the way in which these elements are linked (chemical bonds).
A chemical change is a process, also called a chemical reaction, in which one or more substances are converted into different substances.
The resulting substances are different because their composition is different, since some chemical bonds have been broken and others have been formed, giving rise to a new structure. The chemical formula of each compound product of the chemical change will present a different combination of atoms, in ratio or structure.
It is because of the small size and high electronegativity of nitrogen.
<span>Nitrogen has very small size as compared to the halogens, which have much larger sizes. Due to this, they can not remain bonded to the nitrogen atom and hence are highly unstable. </span>
The answer to your question is C. A solution is a homogeneous mixture composed of two or more substances, so it couldn't have been A and D. Since a solution can't have its substances separated by a chemical means because they are chemically bonded, thus they are able to be separated by physical means
Answer: The given statement is true.
Explanation:
According to the Dalton's law, total pressure of a mixture of gases that do not react with each other is equal to the partial pressure exerted by each gas.
The relationship is as follows.

or, 
where,
....... = partial pressure of individual gases present in the mixture
Also, relation between partial pressure and mole fraction is as follows.

where,
= mole fraction
Thus, we can conclude that the statement Dalton's law of partial pressures states that the total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture, is true.
Answer:
Br- Withdraws electrons inductively
Donates electrons by resonance
CH2CH3 - Donates electrons by hyperconjugation
NHCH3- Withdraws electrons inductively
Donates electrons by resonance
OCH3 - Withdraws electrons inductively
Donates electrons by resonance
+N(CH3)3 - Withdraws electrons inductively
Explanation:
A chemical moiety may withdraw or donate electrons by resonance or inductive effect.
Halogens are electronegative elements hence they withdraw electrons by inductive effect. However, they also contain lone pairs so the can donate electrons by resonance.
Alkyl groups donate electrons by hyperconjugation involving hydrogen atoms.
-NHCH3 and contain species that have lone pair of electrons which can be donated by resonance. Also, the nitrogen and oxygen atoms are very electron withdrawing making the carbon atom to have a -I inductive effect.
+N(CH3)3 have no lone pair and is strongly electron withdrawing by inductive effects.