1.) Write the correct coefficient for K(OH) in the box when the equation is balanced.
_Al2(SO4)3(aq) + __K(OH) (aq) → _Al(OH)3(aq) + _K2(SO4) (aq)

2.) When Ca(OH)2 reacts with HNO3 we get H(OH) and Ca(NO3) and Ca(No3)2 as products

3.) Consider the reaction of sodium and water below and select all the correct statement about it.(More than 1 answer).
2Na(s)+2H2O(l) ->2NaOH(aq)+H2(g)
A) mass is conserved throughout the reaction
B) there are more hydrogen atoms in the reactants than in the products
C) there are as many atoms in the reactants as there are in the products
D) there are more sodium atoms in the reactants than in the products

4.) The balanced chemical equation bellow shows the decomposition of water into hydrogen and oxygen gas
2H2O(l) -> O2(g)+2H2(g)

Part a
-how many atoms are in the reactants
Part B
-how many atoms are in the products

Explanation:

6

1.) Write the correct coefficient for K(OH) in the box when the equation is balanced.

_Al₂(SO₄)₃(aq) + __K(OH) (aq) → _Al(OH)₃(aq) + _K₂(SO₄) (aq)

We need to balance this equation to find the coefficient of KOH in the problem.

Balancing of chemical equation entails conservation of mass;

     To solve this problem, we can set up simple mathematical equations that are solvable;

     aAl₂(SO₄)₃(aq) + bK(OH) (aq) → cAl(OH)₃(aq) + dK₂(SO₄) (aq)

a, b, c and d  are the coefficients that will balance the equation;

    Conserving:

       Al:      2a  = c

        S:      3a   = d

       O:      12a + b  = 3c + 4d

       K:        b  = 2d

let us assume that a = 1;

                                d = 3

                               b  = 6

                               c  = 2

     Al₂(SO₄)₃(aq) +  6K(OH) (aq) →  2Al(OH)₃(aq) +  3K₂(SO₄) (aq)

The coefficient of KOH is 6

Answer :        Ca(OH)₂ + 2HNO₃  →   Ca(NO₃)₂  +  2H₂O

2.) When Ca(OH)2 reacts with HNO3 we get H(OH) and Ca(NO3) and Ca(No3)2 as products:

To write this chemical equation, let us identify the species;

  Reactants:   Ca(OH)₂ and HNO₃

  Products :    Ca(NO₃)₂  and H₂O

 Every chemical equation is of the form;

             Reactants →  Products

         Ca(OH)₂ + 2HNO₃  →   Ca(NO₃)₂  +  2H₂O

The above reaction is a neutralization reaction where acids and base reacts to give salt and water only.

3 .

Reaction equation given:

       2Na(s)        +       2H₂O(l)       →    2NaOH(aq)       +       H₂(g)

A) mass is conserved throughout the reaction

C) there are as many atoms in the reactants as there are in the products

The given reaction obeys the law of conservation of mass. According to this law "in chemical reactions, matter is neither created nor destroyed in the course of a chemical action".

This implies that the total mass of the products of a reacting substances  and products are the same.

                Reactants                    Products

Na                   2                                2

H                     4                                4

O                     2                                2

4.    6atoms , 6 atoms

The given chemical reaction is:

        2H₂O(l)       →    O₂(g)        +          2H₂(g)

      An atom is the smallest indivisible particles of a substance that takes place in chemical reactions.

To find the number of atoms in the reactants and products, let us use the chart below;

Chemical elements                Reactants                  Products

           H                                     2(2) = 4                      2(2)  = 4

           O                                     2(1)  = 2                         2

                                                     6 atoms                  6 atoms

Number of atoms in reactants 6 atoms

Number of atoms in the product 6 atoms

there are no atoms