Answer:

Explanation:
A marble is not a very large object, so a smaller graduated cylinder is a better choice. A 100 milliliter graduated cylinder is not needed to measure the volume of a small marble, so a 25 milliliter graduated cylinder is the best option.
<u>Answer:</u> The relation between the forward and reverse reaction is 
<u>Explanation:</u>
For the given chemical equation:

The expression of equilibrium constant for above equation follows:
.......(1)
The reverse equation follows:

The expression of equilibrium constant for above equation follows:
.......(2)
Relation expression 1 and expression 2, we get:

Hence, the relation between the forward and reverse reaction is 
A beaker of black powder can be a mixture with different substances (i.e gunpowder: a mixture of sulfur, charcoal, etc.), an element which can probably be carbon (known as black), and a compound as well which can be potassium nitrate. Hence, the answer is D.
Answer:
About one valence electron
Explanation:
Obviously, removing that electron gives us [Ar] (same configuration as K1+), which is a noble gas and has 8 electrons. Valence electrons are generally regarded as being 'the outermost electrons' for a given atom. Therefore, with neutral potassium, there is one valence electron
Answer:
N- 1s2 2s2 2p3
Mg- 1s2 2s2 2p6 3s2
O- 1s2 2s2 2p4
F- 1s2 2s2 2p5
Al-1s2 2s2 2p6 3s2 3p1
Explanation:
Order of decreasing atomic radius
Mg,Al, N,O,F
Order of increasing ionization energy
Mg,Al, N,O,F
Reason:
Atomic radius decreases with increase in nonmetallic character. Looking at the electronic configurations, as effective nuclear charge increases, the atom becomes smaller and the attractive force between the nucleus and the outermost electrons increases. Hence, the radius of the atom decreases and ionization energy increases. Note that the addition of more orbital electrons implies addition of more nuclear charge since the both must exactly balance for the atom to remain electrically neutral. The more the electrons in the outermost shell, the higher the first ionization energy.