Explanation:
Atomic size is defined as the distance between the nucleus and valence shell of an atom. Valence shell is the outermost shell of an atom.
When we move across a period in a periodic table then there will occur a decrease in atomic size of the atoms. But when we move across a group in a periodic table then there will occur an increase in atomic size of the atom.
Hydrogen is a period 1 element, oxygen is a period 2 element, chlorine is a period 3 element and bromine is a period 4 element.
Therefore, given elements are arranged in order of increasing atomic size as follows.
H < O < Cl < Br
Burning a magnesium ribbon in the air is an addition reaction while heating potassium manganate 7 is a decomposition reaction.
<h3>Addition and decomposition reactions</h3>
Magnesium burns in air to produce magnesium oxide as follows:

Potassium manganate 7 burns to produce multiple products as follows:

Thus, the MgO will be heavier than Mg. On the other hand,
will be less heavy than
.
More on reactions can be found here: brainly.com/question/17434463
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Answer : The ratio of
to
is, 
Solution : Given,

= 0.21 atm
The given equilibrium reaction is,

The expression of
will be,

Now put all the given values in this expression, we get:



Therefore, the ratio of
to
is, 
Answer: Option (A) is the correct answer.
Explanation:
Condensation is defined as the process in which vapors or gaseous phase changes into liquid phase.
Freezing is the process in which liquid phase changes into solid phase.
Evaporation is the process in which liquid phase changes into vapors or gaseous phase.
Melting is the process in which solid phase changes into liquid phase.
Therefore, we can conclude that names for given phase changes A and B is that A is condensation and B is freezing.
The computation for this problem is:
(1.55x10^4 / 1.0x10^3) x 19.8 mm Hg
= 15.5 x 19.88 mm Hg
= 308.14 mm Hg decrease
= 308.14 x 0.05 C = 15.407 deg C
deduct this amount to 100
100 – 15.407 = 84.593 C
ANSWER: 85 deg C (rounded to 2 significant figures)