Answer:
(1) Chloroplast
Explanation:
Cells of living organisms are made up of certain function-specific structures called ORGANELLES. Some organelles are present in plant cells and absent in animal cells and vice versa. In a plant cell, one notable organelle that allows it perform the photosynthetic process is the CHLOROPLAST.
However, the chloroplast is predominantly found in the LEAF part of a plant. This is because leaf cells are the site of photosynthesis. Hence, according to this question, Joe would be able to tell whether the plant cell was from the leaf or the root by looking for CHLOROPLAST as a differentiating factor in each cell.
Answer:

Explanation:
N2(g)+O2(g)⇌2NO(g), 
N2(g)+2H2(g)⇌N2H4(g), 
2H2O(g)⇌2H2(g)+O2(g), 
If we add above reaction we will get:
2N2(g)+2H2O(g)⇌2NO(g)+N2H4(g) Eq (1)
Equilibrium constant for Eq (1) is 
Divide Eq (1) by 2, it will become:
N2(g)+H2O(g)⇌NO(g)+1/2N2H4(g) Eq (2)
Equilibrium constant for Eq (2) is 

All chemical reactions have a conversation of mass and energy.
Because:- There are only two laws for conversation in a chemical reaction. The conversation of mass, no mass can be created nor destroyed. Also, the law of conversation of mass states that no energy can be created nor destroyed in a chemical reaction. The charge can obviously change because they can bond and change charges.
An element is a mixture of two isotopes. One isotope has an atomic mass of 34.969 amu and an abundance of 64.88%. The other isotope has an atomic mass 36.966 amu.