Mno2 + 4hcl reacts to form mncl2 + cl2 + 2h2o if .86 mol of mno2 and 48.2 g of hcl react, which reactant is the limiting reagent

HCl:

m=48,2g
M=36,5g/mol

n = m/M = 48,2g / 36,5g/mol = 1,32mol

1mol          : 4mol
MnO₂        + 4HCl ⇒ MnCl₂ + Cl₂ + 2H₂O
0,86mol     :  1,32mol
                     limiting reagent 
0,33 will react

HCl is limiting reagent.

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na