<u>Answer:</u> The reactant ratio in the given chemical equation will be: 
<u>Explanation:</u>
Mole ratio is defined as the ratio of the amount of moles of two substances that are participating in a chemical reaction.
In the given chemical equation:

The reactants are Fe and
and the product is 
The mole ratio is basically the stoichiometric ratio of the chemical compounds taking part in a chemical reaction.
The mole ratio of reactants is stoichiometric ratio of Fe and
, which is:

Hence, the reactant ratio in the given chemical equation will be: 
Answer: 4.21×10⁻⁸
Explanation:
1) Assume a general equation for the ionization of the weak acid:
Let HA be the weak acid, then the ionization equation is:
HA ⇄ H⁺ + A⁻
2) Then, the expression for the ionization constant is:
Ka = [H⁺][A⁻] / [HA]
There, [H⁺] = [A⁻], and [HA] = 0.150 M (data given)
3) So, you need to determine [H⁺] which you do from the pH.
By definition, pH = - log [H⁺]
And from the data given pH = 4.1
⇒ 4.10 = - log [H⁺] ⇒ [H⁺] = antilog (- 4.10) = 7.94×10⁻⁵
4) Now you have all the values to calculate the expression for Ka:
ka = 7.94×10⁻⁵ × 7.94×10⁻⁵ / 0.150 = 4.21×10⁻⁸
For a p type of semiconductor we need a dopant which is from 13th group in periodic table
Al , B, Ga, In Tl
So the correct element will be In : Indium
The other elements belongs to 15th group and hence will give n type semiconductor
The molecular formula =C₆H₁₂O₆
<h3>Further explanation</h3>
Given
6.00 g of a certain compound X
The molecular molar mass of 180. g/mol
CO₂=8.8 g
H₂O=3.6 g
Required
The molecular formula
Solution
mass C in CO₂ :
= 1.12/44 x 8.8
= 2.4 g
mass H in H₂O :
= 2.1/18 x 3.6
= 0.4 g
Mass O in compound :
= 6-(2.4+0.4)
= 3.2 g
Mol ratio C : H : O
= 2.4/12 : 0.4/1 : 3.2/16
= 0.2 : 0.4 : 0.2
= 1 : 2 : 1
The empirical formula : CH₂O
(CH₂O)n=180 g/mol
(12+2+16)n=180
(30)n=180
n=6
(CH₂O)₆=C₆H₁₂O₆
Photosynthesis: The process of making something ( carbohydrates ) with light
CO+H2O &Sunlight=O2+C6H6O12