Hydrogen boils at 20k. what is the boiling point of hydrogen on the celsius scale

Celsius scale is related to kelvin scale by the following equation,

⁰C = K-273

°C = K-273  

So as here temperature is given in kelvin, so it can be converted into celsius as follows:

So 20 K = 20K-273 °C  

= -253 °C .

So, the 20 K temperature equals to -253 °C.

So , -253 °C is equals to  20 K or 20 K temperature equals to -253 °C.

the answer is true. hope it .

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.