Which ion do most bases form?

Hydroxide OH-

Explanation:

Hydroxide OH- is the most common ion bases form from under HSAB

Examples

LiOH - lithium hydroxide

NaOH - sodium hydroxide

KOH - potassium hydroxide

RbOH - rubidium hydroxide

CsOH - cesium hydroxide

Ca(OH)2 - calcium hydroxide

Sr(OH)2 - strontium hydroxide

Ba(OH)2 - barium hydroxide

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2