The initial concentration of C2H6N2 in the first-order reaction C2H6N2→N2+C2H6 is 0.427 M. After 30. seconds, the concentration of C2H6N2 is 0.395 M. What is the rate constant k for the reaction?

2.6×10^-3 mols-1

Explanation:

From

k= 2.303/t × log[A]o/[A]t

Time taken t= 30 seconds

Initial concentration [A]o= 0.427M

Concentration at time (t) [A]t= 0.395M

k= 2.303/30 ×log[0.427]/[0.395]=2.6×10^-3 mols-1

We can observe physical properties of elements and compounds without changing the substance.

Examples of physical properties: Density, color, boiling point, state of matter, appearance: dull or shiny, etc. 

But we can also observe and measure chemical properties by reacting a substance with something else. For example, like mixing baking soda and vinegar together. The vinegar reacts with the baking soda and produces carbon dioxide: a new substance. 

Some examples of chemical properties: Flammability, amount of heat that is released during combustion, toxicity (how much damage it causes to other organisms), radioactivity, and ability to oxidize (when you have metal that becomes rusty looking).