Apolyatomic ion that contains two hydrogen atoms is called

A polyatomic ion that contains two hydrogen atoms is called a dihydrogen.
 It is a rule for non-metallic polyatomic molecules to make use of such prefixes before each element's name. 

A polyatomic ion that contains two hydrogen atoms is called a Dihydrogen

Explanation:

Given:

At 25∘C and total pressure of 1.0 atm,Partial pressure of Oxygen, PO2 = 0.21 atm and,Partial pressure of nitrogen, PN2 = 0.78 atm.

At 50∘C and 1 atm,

Solubility of oxygen = 27.8 mg/ L and solubility of nitrogen = 14.6 mg/ L

Apply the Henry law, Pi = H x Ciequation1

Where Pi is the partial pressure of species 'i' and H is Henry constant and Ci is the solubility of species 'i'., Henry constant for oxygen is HO2 = 769.23 L atm/mol

From the equation (1) the solubility of oxygen at 25∘C;

= 0.21/769.23 = 0.000273mol/L or C'(O2) = 0.000273 X 32g X gL/mol X mol/L = 8.736mg

Therefore ; the solubility of oxygen at 50oC and pressure @ 1 atm,

= 27.8 X 1L X mg/L = 27.8mgbut, the partial pressure of oxygen in the solution is 0.21 atm, hence the solubility will be decreased to 27.8 x 0.21 atm/1 atm = 5.838mgfrom 25∘C - 50∘C ; 8.736 - 5.838 = 2.898 mg of oxygen should be bubble out.

Hence, Volume of oxygen = Mass/density = 2.898mg/1.429mg/L = 2.027mL

Similarly, For nitrogen, At 50∘C and 1 atm,solubility of nitrogen = 14.6 mg/ LHence, Henry constant for Nitrogen is HN2 = 1639.34 L atm/mol,

From the equation (1) the solubility of nitrogen at 25oC ;

C(N2) = 0.78/1639.34 = 0.0004758mol/Lor Ci = 0.0004758mol/L X 28g X 1L/mol X mol/L = 13.322mg

Hence, The solubility of Nitrogen at 50oC and pressure @ 1 atm,;

Ci = 14.6 X 1L X mg/L = 14.6mg

But the partial pressure of Nitrogen in the solution is 0.78 atm, hence the solubility will be reduced to 14.6 x 0.78 atm/1 atm = 11.388 mg

warming from 25∘C - 50∘C; 13.322 - 11.388 = 1.934 mg of Nitrogen

Hence, volume of nitrogen = mass/density = 1.934mg/1.2506mg/L= 1.55mL