0.0015 kilometers is for sure the answer!
Nitrogen is often used for the storage of semen samples for artificial insemination of cattle. Nitrogen is used to maintain a dry inert atmosphere over chemicals during storage, reaction or processing. Used in brewing, soft drinks and wine-making industries to exclude air from the product and de-aerate water.
Water boils when its vapor pressure equals the prevailing atmospheric pressure over the water. In order for water to boil at 50 ºC, the pressure over the water would need to be reduced to a point greater equal to the vapor pressure of the water (92.5 torr).
Take the atomic mass of silicon and put it over one. Then set that equal to x over 4.8 x 1026. X will equal to the weight of silicon in grams.
