We use the gas law named Charle's law for the calculation of the second temperature. The law states that,
V₁T₂ = V₂T₁
Substituting the known values,
(0.456 L)(65 + 273.15) = (3.4 L)(T₁)
T₁ = 45.33 K
People had asked this many times and that is why they came up with methods and standards that will answer these type of questions. You can look it up in the NIST or the National Institute for Standards and Technology.
Solute - the substance that dissolves into the solvent to produce a homogenous mixture
Solvent - the substance in which a solute dissolves to produce a homogeneous mixture
it should either be 5 or 10
Adding the number of protons by the number of neutrons