Reactant C is the limiting reactant in this scenario.
Explanation:
The reactant in the balanced chemical reaction which gives the smaller amount or moles of product is the limiting reagent.
Balanced chemical reaction is:
A + 2B + 3C → 2D + E
number of moles
A = 0.50 mole
B = 0.60 moles
C = 0.90 moles
Taking A as the reactant
1 mole of A reacted to form 2 moles of D
0.50 moles of A will produce
= 
thus 0.50 moles of A will produce 1 mole of D
Taking B as the reactant
2 moles of B reacted to form 2 moles of D
0.60 moles of B reacted to form x moles of D
= 
x = 2 moles of D is produced.
Taking C as the reactant:
3 moles of C reacted to form 2 moles of D
O.9 moles of C reacted to form x moles of D
= 
= 0.60 moles of D is formed.
Thus C is the limiting reagent in the given reaction as it produces smallest mass of product.
1 mol is equal to 6.02×10∧23 molecules.
first put in the calculator 4.81042 × 6.02 then hit EXP or 2nd then EE. (Depends on the type of calculator). then put in 23 and press equal.
The calculator will says 2.89587284×10∧24.
So the answer will be 2.90×10∧24.
I mot sure if the 2.90 is correct but it is close to the answer. it really depends how you want to round it. As long as the decimals are close the answer doesn't matter. Hope this helps. Please mark as Brainliest.