Answer:
D
Explanation:
From periodic table : proton number 19 corresponds to K (potassium)
which is very reactive with water
Al2Se3 is your chemical formula
Hope this helps
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C, potassium. Hope this helps.
Answer: True
Explanation:
The matter exists as solid, liquid or gas. These are called the states of matter. The change of matter from one state to another can be achieved by heating or cooling.
The solid state can be converted into liquid state by providing heat to solid. The heat will make the particles move farther, resulting into liquid state.
Similarly when liquid state is provided heat, it changes to gaseous state. The heat will make the particles move much more faster.
Thus the statement that when heat flows to an object, it can change states is True.
Explanation:

The maximum wavelength of light that can cause this reaction is 420 nm.
a) The wavelength given lies in the range of visible light range that is from 400 nano meters to 700 nano meters.
The light with wavelength of 420 nm is found in the range of visible light.
b)The maximum strength of a bond :

where,
E = energy of photon = Energy required to break single molecule of nitrogen dioxide
h = Planck's constant = 
c = speed of light = 
= wavelength = 


Energy required to break 1 mole of nitrogen dioxide molecules:


(1 J = 0.001 kJ )
285.13 is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 420-nm light.
c) the photodissociation reaction showing Lewis-dot structures is given in an image attached.