I really need help with these chemistry questions pleasee

The answer to your question is given below

Explanation:

8. The equation for the reaction is given below:

Mg3N2 + H2O –> Mg(OH)2 + NH3

Number of reactant atoms before balancing:

Mg = 3

N = 2

H = 2

O = 1

Number of product atoms before balancing:

Mg = 1

N = 1

H = 5

O = 2

Now, let us balanced the equation.

Mg3N2 + H2O –> Mg(OH)2 + NH3

There are 3 atoms of Mg on the left side and 1 atom on the right side. It can be balance by putting 3 in front of Mg(OH)2 as shown below:

Mg3N2 + H2O –> 3Mg(OH)2 + NH3

There are 2 atoms of N on the left side and 1 atom on the right side. It can be balance by putting 2 in front of NH3 as shown below:

Mg3N2 + H2O –> 3Mg(OH)2 + 2NH3

There 2 atoms of H on the left side and a total of 12 atoms on the right side. It can be balance by putting 6 in front of H2O as shown below:

Mg3N2 + 6H2O –> 3Mg(OH)2 + 2NH3

Now the equation is balanced.

Number of reactant atoms after balancing:

Mg = 3

N = 2

H = 12

O = 6

Number of product atoms after balancing:

Mg = 3

N = 2

H = 12

O = 6

9. When methane react with steam, carbon dioxide and hydrogen gas are produced as shown below:

CH4 + H2O –> CO + H2

Now, let us balance the equation. This is illustrated below:

There are a total of 6 atoms of H on the left side and 2 atoms on the right side. It can be balance by putting 3 in front of H2 as shown below:

CH4 + H2O –> CO + 3H2

Now the equation is balanced.

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

c (diamond),

sio2 (quartz)