20 points 2 questions can you answer them
1 which of the following reactions is a synthesis reaction?
n2 + 3h2 → 2nh3
mgi2 + br2 → mgbr2 + i2
kclo3 → kcl + o2
hcl + naoh → nacl + h2o
2 suppose that the half-life of an element is 1000 years. how many half-lives will it take before one-eighth of the original sample remains?
8
125
12.5
3

Answer 1 : The synthesis reaction is,

Explanation :

Synthesis reaction : It is a type of reaction in which the reactants present in elemental state react to give a single product.

(1)

This is a synthesis reaction.

(2)

This is a single displacement reaction in which the most reactive element displaces the least reactive element.

(3)

This is a decomposition reaction in which larger reactant decomposes to give two or more products.

(4)

This is a neutralization reaction in which an acid and a base react to give a salt and water as a product.

Answer 2 : The number of half-lives it take will be, 3

Formula used :

where,

a = amount of reactant left after n-half lives =

= Initial amount of the reactant

n = number of half lives

Putting values in above equation, we get:

n = 3

Therefore, the number of half-lives it take will be, 3