To find density we have to know the values of density and mass. Here mass is given which i 180g.
we know the formula to find the density is:
Density = Mass / volume
so the density will be 180 / volume = 180g per unit volume
if we know the volume, we can find exact value of density.
0.0036g of NH4+ x 1mol of NH4+/18.04g of NH4+ x 6.02*10^23 electrons of NH4+/1mol of NH4+
= 1.20 x 10^20 electrons of NH4+
Answer : The correct answer is a) an exothermic reaction that releases energy.
Combustion reaction is generally referred as burning or when hydrocarbon reaction with oxygen to produce carbon dioxide and water . Combustion reaction releases energy. Example :
CH₄ + O₂ → CO₂ + H₂O + Energy or heat .
The reaction which releases energy or heat are known as Exothermic reactions .
Since it says hot dogs and hamburgers are cooked means they are undergoing combustion chemical reaction and so they are exothermic reactions. So option a) an exothermic reaction which releases energy is correct .
Answer : The correct option is, (D) double replacement reaction
Explanation :
Synthesis reaction : A chemical reaction where multiple substances or reactants combine to form a single product.
It is represented as,

Decomposition reaction : A chemical reaction in which larger reactant decomposes to give two or more than two products.
It is represented as,

Single replacement reaction : A chemical reaction in which the more reactive element replace the less reactive element.
It is represented as,

In this reaction, A is more reactive element and B is less reactive element.
Double replacement reaction : It is a type of chemical reaction where a positive cation and a negative anion of two reactants exchange places to form two new products.
It is represented as,

(X and A are the cations, Y and B are the anions)
The given reaction is:

This reaction is a double displacement reaction.
Answer : The question is incomplete, the complete question is attached in answer
To calculate the displacement by Ann's driving from north of her house to south;
we have the data as
In north - 10 km
in south - 5 km
total - 15 km
So we can calculate the displacement, which will be,
10 - 5 =
5 km.Hence, the displacement will be
5 km