When oxygen (o2) is passed through an electrical spark (lightning is a good natural source of an electrical spark), ozone (o3) is formed. when the equation is balanced, the coefficient of the ozone


This the chemical equation of the reaction of Al and HCl

Al +  HCl → AlCl3 + H2 (g)

When you balance the atomos you get:

2Al +  6HCl → 2AlCl3 + 3H2 (g)  you can check that here you have the same number of atoms of Al, H, and Cl in both sides.

The coefficients are:

2 for Al, 6 for HCl, 2 for AlCl3 , and 3 for H2.

Then, the answer is: the coefficient of HCl is 6
The reaction is as follow,

                   Ca(OH)₂  +  Al₂(SO₄)₃    →     CaSO₄  +  Al(OH)₃

Ca are balance on both sides, 

There are 2 Al at left side and one at right so, multiply Al(OH)₃ by 2 to balance,
                   Ca(OH)₂  +  Al₂(SO₄)₃    →     CaSO₄  +  2 Al(OH)₃

Now, Ca and Al are balanced, now balance SO₄, which is 3 at left hand side and one at right hand side, so multiply CaSO₄ on right side by 3, so,

                   Ca(OH)₂  +  Al₂(SO₄)₃    →     3 CaSO₄  +  2 Al(OH)₃

Again Ca got imbalance, so multiply Ca(OH)₂ by 3 to balance Ca, So,

                   3 Ca(OH)₂  +  Al₂(SO₄)₃    →     3 CaSO₄  +  2 Al(OH)₃

The Equation is balance now with respect to every element.

          The Ratio is 3 : 1 : 3 : 2, so, Option-G is correct.
The correct option is 2
H on left = 2 on right 2 
O on left = 1 on right = 1 
eqn is balanced as is thus a 1 coeffecient

The coefficient of H3PO4 is 1


The equation is H3PO4(aq) + NaOH (aq) → Na3PO4(aq) + H2O (l)

To balance the reaction, we first balance the Na atoms: On the right there are 3 Na atoms, so on the left we multiply NaOH by 3

The number of P atoms on the left is 1, the number of the P atoms on the right is also 1. So, this is already balanced.

On the left there are 6 H atoms, on the right we have 2H atoms, so e have to multiply H2O by 3.

On the left we have 7 O atoms, on the right, now we have also  7O atoms.

So this is already balanced.

The fully balanced reaction is H3PO4 (aq) + 3NaOH(aq) → Na3PO4(aq) + 3H2O(l)

The coefficient of H3PO4 is 1

The answer to your question is:  4


                      __C3H4   +    _4O2    →     _3CO2    +    2H20

                                          3      C   3

                                          4     H   4

                                         8       O   8

Ca(s) + 2H_2O \rightarrow Ca(OH)_2 +H_2



In a balanced chemical equation, the number of atoms of each element are equal on both sides.

Ca(s) + H_2O \rightarrow Ca(OH)_2 +H_2

No. of atoms of Ca in left hand side = 1

No. of atoms of Ca in right hand side = 1

So, no. of atoms of Ca is balanced


No. of atoms of O in left hand side = 1

No. of atoms of O in right hand side = 2

Now multiply H2O with 2

Ca(s) + 2H_2O \rightarrow Ca(OH)_2 +H_2

No. of atoms of O are balanced on each side

No. of atoms of H in left hand side = 4

No. of atoms of H in right hand side = 4

Now, each element is balanced

So coefficient of H2O after balancing = 2

The correct answer is Option E.


Every balanced chemical equation follows law of conservation of mass.

This law states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.  

This also means that total mass on the reactant side must be equal to the total mass on the product side.

The balanced chemical equation for the reaction of aluminium and water follows:

2Al(s)+6H_2O(l)\rightarrow 2Al(OH)_3(s)+3H_2(g)

The coefficient of Aluminium is 2.

Hence, the correct answer is Option E.



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.

The balanced equation for the given reaction is:

Ba(s)+2HCl(aq)\rightarrow BaCl_2+H_2(g)

Thus the coefficient for HCl is 2.



The balanced equation is

3O2 >  2O3.

Do you know the answer?

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