You have to use Avogadro's number (6.02x10^23 molecules/mole) to find the number of moles each reactant starts off with.
moles of Fe and O₂:
12 atoms/(6.02x10^23 atoms/mole)=1.99x10^-23 mol Fe
6 molecules/(6.02x10^23 molecules/mole)=9.967x10^-24 mol <span>O₂
</span>Then you find the limiting reagent by finding how much product each given amount of reactant can make. Which ever one produces the least amount of product is the limiting reagent.
amount of Fe₂O₃ produced:
<span>(1.99x10^-23 mol Fe)x(2mol/4mol)= 9.967x10^-24mol Fe</span>₂O₃<span>
</span>(9.967x10^-24 mol O₂)x(2mol/3mol)= 6.645x10^-24 mol Fe₂O₃<span>
</span>since oxygen produces the leas amount of product, oxygen is the limiting reagent. since we know that oxygen is the limiting reagent we can use the amount of product formed with oxygen to find the amount of iron used.
6.645x10^-24 mol Fe₂O₃x(4mol/2mol)=1.329x10^-23 mol Fe consumed
<span> find the amount left over by subtracting the original amount of Fe by the amount consumed in the reaction.
</span>1.993x10^-23-1.329x10^-23= 6.645x10^-23mol Fe left
find the number of atoms by multiplying that by Avogadro's number.
<span>(6.645x10^-23mol)x(6.02x10^23 atoms/mol)=4 atoms
</span>therefore 4 atoms of Fe will be left over after the reaction happens.
I hope this helps.
Depression in freezing point (Δ
) =
×m×i,
where,
= cryoscopic constant =
,
m= molality of solution = 0.0085 m
i = van't Hoff factor = 2 (For
)
Thus, (Δ
) = 1.86 X 0.0085 X 2 =
Now, (Δ
) =
- T
Here, T = freezing point of solution
= freezing point of solvent =
Thus, T =
- (Δ
) = -
Answer:
pH = 10.75
Explanation:
To solve this problem, we must find the molarity of [OH⁻]. With the molarity we can find the pOH = -log[OH⁻]
Using the equation:
pH = 14 - pOH
We can find the pH of the solution.
The molarity of Ca(OH)₂ is 2.8x10⁻⁴M, as there are 2 moles of OH⁻ in 1 mole of Ca(OH)₂, the molarity of [OH⁻] is 2*2.8x10⁻⁴M = 5.6x10⁻⁴M
pOH is
pOH = -log 5.6x10⁻⁴M
pOH = 3.25
pH = 14-pOH
<h3>pH = 10.75</h3>
Answer:
Ka = 6.02x10⁻⁶
Explanation:
The equilibrium that takes place is:
We <u>calculate [H⁺] from the pH</u>:
- [H⁺] =
Keep in mind that [H⁺]=[A⁻].
As for [HA], we know the acid is 0.66% dissociated, in other words:
We <u>calculate [HA]</u>:
Finally we <u>calculate the Ka</u>:
- Ka =
![\frac{[9.12x10^{-4}]*[9.12x10^{-4}]}{[0.138]}](https://tex.z-dn.net/?f=%5Cfrac%7B%5B9.12x10%5E%7B-4%7D%5D%2A%5B9.12x10%5E%7B-4%7D%5D%7D%7B%5B0.138%5D%7D)
= 6.02x10⁻⁶
Answer:
the symbol of an iron is Fe (ferous, feric).
