Answer:
we need 6.0 moles of zinc (Zn)
Explanation:
Step 1: Data given
Number of moles ZnO produced = 6.0 moles
Step 2: The balanced equation
2 Zn + O2 → 2 ZnO
For 2 moles Zinc we need 1 mol Oxygen to produce 2 moles Zinc oxide
Step 3: Calculate moles zinc
For 2 moles Zn we need 1 mol O2 to produce 2 moles ZnO
For 6.0 moles 2nO produced, we need 6.0 moles of zinc (Zn) and 3.0 moles of O2 to react.
Yield is the measured amount of a product obtained from a reaction.
Hope that's helpful
Characteristic properties are used because the sample size and the shape of the substance does not matter.
Answer:
a) The relationship at equivalence is that 1 mole of phosphoric acid will need three moles of sodium hydroxide.
b) 0.0035 mole
c) 0.166 M
Explanation:
Phosphoric acid is tripotic because it has 3 acidic hydrogen atom surrounding it.
The equation of the reaction is expressed as:

1 mole 3 mole
The relationship at equivalence is that 1 mole of phosphoric acid will need three moles of sodium hydroxide.
b) if 10.00 mL of a phosphoric acid solution required the addition of 17.50 mL of a 0.200 M NaOH(aq) to reach the endpoint; Then the molarity of the solution is calculated as follows

10 ml 17.50 ml
(x) M 0.200 M
Molarity = 
= 0.0035 mole
c) What was the molar concentration of phosphoric acid in the original stock solution?
By stoichiometry, converting moles of NaOH to H₃PO₄; we have
= 
= 0.00166 mole of H₃PO₄
Using the molarity equation to determine the molar concentration of phosphoric acid in the original stock solution; we have:
Molar Concentration = 
Molar Concentration = 
Molar Concentration = 0.166 M
∴ the molar concentration of phosphoric acid in the original stock solution = 0.166 M