A catalyst is: a chemical found in leaves
a chemical which promotes a chemical reaction
a chemical which reacts with sunlight
a cell with chlorophyll

The correct option is B.

A Catalyst is a chemical which promotes or speed up a chemical reaction without undergoing any chemical reaction itself.

for example : potassium permanganate - Hydrogen peroxide will decompose into water and oxygen gas in the presence of KMnO4.

_____________________________

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.

the maximum mass of nh3 is nh3 in grams