Answer:
The radii of potassium is 231 pm
Explanation:
Atomic radii trend along group:
As we move down the group atomic radii increased with increase of atomic number. The addition of electron in next level cause the atomic radii to increased. The hold of nucleus on valance shell become weaker because of shielding of electrons thus size of atom increased.
The given elements are present in same group i.e group one,
Li 152 pm
Na 186 pm
K
Rb 244 pm
The radii of potassium must be greater than sodium and smaller than rubidium.
Thus the value must be between 186 pm - 244 pm
it means the radii of potassium is 231 pm.
I believe the answer is salt. because it is a compound of two distinct elements that can be broken down without changing the properties of substance.
A pure substance is a substance that are made up of only one type of an atom or one type of a molecule. Pure substances may be further broken down into elements and compounds.
Aluminum hydroxide 
can behave as a base and neutralize sulfuric acid 
as in the following equation:
(Balanced)
(a)
. Thus the ratio between the number of moles of the two reactants available:
![n(\text{Al}(\text{OH})_3, \text{supplied}) / n(\text{H}_2\text{SO}_4, \text{supplied})\\= [m(\text{Al}(\text{OH})_3)/ M(\text{Al}(\text{OH})_3)] / [n(\text{H}_2\text{SO}_4) / M(\text{H}_2\text{SO}_4)]\\= [23.7 / (26.98 + 3 \times(16.00 + 1.008))]/[29.5 / (2 \times 1.008 + 32.07 + 4 \times 16.00)]\\\approx 1.01](https://tex.z-dn.net/?f=n%28%5Ctext%7BAl%7D%28%5Ctext%7BOH%7D%29_3%2C%20%5Ctext%7Bsupplied%7D%29%20%2F%20n%28%5Ctext%7BH%7D_2%5Ctext%7BSO%7D_4%2C%20%5Ctext%7Bsupplied%7D%29%5C%5C%3D%20%5Bm%28%5Ctext%7BAl%7D%28%5Ctext%7BOH%7D%29_3%29%2F%20M%28%5Ctext%7BAl%7D%28%5Ctext%7BOH%7D%29_3%29%5D%20%2F%20%5Bn%28%5Ctext%7BH%7D_2%5Ctext%7BSO%7D_4%29%20%2F%20M%28%5Ctext%7BH%7D_2%5Ctext%7BSO%7D_4%29%5D%5C%5C%3D%20%5B23.7%20%2F%20%2826.98%20%2B%203%20%5Ctimes%2816.00%20%2B%201.008%29%29%5D%2F%5B29.5%20%2F%20%282%20%5Ctimes%201.008%20%2B%2032.07%20%2B%204%20%5Ctimes%2016.00%29%5D%5C%5C%5Capprox%201.01)
The value of this ratio required to lead to a complete reaction is derived from coefficients found in the balanced equation:
The ratio for the complete reaction is smaller than that of the reactants available, indicating that the species represented on the numerator, , is in excess while the one on the denominator, , serves as the limiting reagent.
(b)
The quantity of water produced is dependent on the amount of limiting reactants available. 
of sulfuric acid is supplied in this reaction as the limiting reagent. 
moles of water molecules are produced for every 
moles of sulfuric acid consumed. The reaction would thus give rise to 
of water molecules, which have a mass of 
.
(c)
(d)
The quantity of , the reactant in excess, is dependent on the number of moles of this species consumed in the reaction and thus the quantity of the limiting reagent available. The consumption of every moles of sulfuric acid, the limiting reagent, removes 
moles of aluminum hydroxide from the solution. 
of sulfuric acid is initially available as previously stated such that 
, or 
, of would be eventually consumed.
of would thus be in excess by the end of the reaction process.
I think it’s SO3 I’m not quite sure though
