Answer: 
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here iron is having an oxidation state of +3 called as
cation and oxide
is an anion with oxidation state of -2. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral
.
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

Answer: The correct option is option d
Explanation - The mean deal with science is that it allows people to carry on research in an organized manner to find or make new discoveries and inventions.
The basic purpose of science is to try new things or ways to get an outcome by constant perseverance on research and negating the ways that don't work thus giving and improving knowledge of what is correct and what is not to make a new Discovery or invention.
Answer:
3.41 x10⁶ torr
Explanation:
To solve this problem we need to remember the equivalency:
1 torr = 133.322 Pa
Then we can proceed to<u> convert 4.55×10⁸ Pa into torr.</u> To do that we just need to multiply that value by a fraction number, putting the unit that we want to convert <em>from</em> in the <em>denominator</em>, and the value we want to convert <em>to</em> in the <em>numerator</em>:
4.55x10⁸ Pa *
3.41 x10⁶ torr
Element Atomic Number Valency
Valency of Hydrogen 1 1
Valency of Helium 2 0
Valency of Lithium 3 1
Valency of Beryllium 4 2
Valency of Boron 5 3
Valency of Carbon 6 4
Valency of Nitrogen 7 3
Valency of Oxygen 8 2
Valency of Fluorine 9 1
Valency of Neon 10 0
Valency of Sodium (Na) 11 1
Valency of Magnesium (Mg) 12 2
Valency of Aluminium 13 3
Valency of Silicon 14 4
Valency of Phosphorus 15 3
Valency of Sulphur 16 2
Valency of Chlorine 17 1
Valency of Argon 18 0
Valency of Potassium (K) 19 1
Valency of Calcium 20 2
Valency of Scandium 21 3
Valency of Titanium 22 4
Valency of Vanadium 23 5,4
Valency of Chromium 24 2
Valency of Manganese 25 7, 4, 2
Valency of Iron (Fe) 26 2, 3
Valency of Cobalt 27 3, 2
Valency of Nickel 28 2
Valency of Copper (Cu) 29 2, 1
Valency of Zinc 30 2