Answer:
Explanation:
1. Virus's are hard to detect because of their simple construction.
2. Some mutate very easily.
3. It is hard to isolate the virus and kill it without doing damage to the host.
Answer:
900 J/mol
Explanation:
Data provided:
Enthalpy of the pure liquid at 75° C = 100 J/mol
Enthalpy of the pure vapor at 75° C = 1000 J/mol
Now,
the heat of vaporization is the the change in enthalpy from the liquid state to the vapor stage.
Thus, mathematically,
The heat of vaporization at 75° C
= Enthalpy of the pure vapor at 75° C - Enthalpy of the pure liquid at 75° C
on substituting the values, we get
The heat of vaporization at 75° C = 1000 J/mol - 100 J/mol
or
The heat of vaporization at 75° C = 900 J/mol
Relative atomic mass of NaCl=23+35.5=58.5
2000kg / 58.5 = mass per relative atomic mass = 34.188
34.188 * atomic mass of Na, 34.188 * 23 = 786.325... = 790 kg (2s.f.)
For many (but not all) problems, you can simply round the atomic weights and the molar mass to the nearest 0.1 g/mole. HOWEVER, make sure that you use at least as many significant figures in your molar mass as the measurement with the fewest significant figures. In other words, never let your molar mass be the measured value that determines how many signficant figures to use in your answer!
