The answer is probably c i guess
The answer is catalyst.
A catalyst is characterized by acceleration the rate of a chemical reaction but not modifiy the equilibrium, which is what k represents (the constant of equilibrium of the reaction).
The catalyst manages that the reaction goes through a different pathway, with a lower activation energy, so the transition compound is reached faster and the whole reaction goes faster, but the final species and their equilibriium concentrations do not change.
Standard temperature is 273 K
Standard pressure is 1 atm
We use the ideal gas equation to find out density of nitrogen gas in g/L
Ideal gas equation:
Molar mass of 
Pressure = 1 atm
Temperature = 273 K
= 1.25 g/L
Therefore, density of nitrogen gas at STP is 1.25 g/L
Physical Properties: Sodium bicarbonate is an odorless, white crystalline solid or fine powder. It has a slightly alkaline taste. Its density is 2.20 g mL-1 and it decomposes in temperatures above 50 ºC. The decomposition yields to sodium carbonate. It is highly soluble in water and poorly soluble in acetone and methanol. It is insoluble in ethanol.
Chemical Properties: Sodium bicarbonate is an amphoteric compounds, it means the compound has a character acids an basic at the same time. It is highly soluble in water, resulting in a slighty alkaline solution.
i hope this part helps i will continue to research on Toothpaste's properties
