The formula of Density is known as:
Density = mass/volume
Units: g/cm^3
Hope this helps!
        
             
        
        
        
Explanation:
Knowing the number of valence electrons in one of the alien elements helps in identifying it because the number of valence electrons can help categorize the alien element. Similar elements have the same valence electrons and knowing the category of the element can help further analyze the element.
 
        
                    
             
        
        
        
Answer: There are now 2.07 moles of gas in the flask.
Explanation:
 
P= Pressure of the gas = 697 mmHg = 0.92 atm  (760 mmHg= 1 atm)
V= Volume of gas = volume of container = ?
n = number of moles = 1.9
T = Temperature of the gas = 21°C=(21+273)K= 294 K   (0°C = 273 K)
R= Value of gas constant = 0.0821 Latm\K mol
 
When more gas is added to the flask. The new pressure is 775 mm Hg and the temperature is now 26 °C, but the volume remains same.Thus again using ideal gas equation to find number of moles.
 
P= Pressure of the gas = 775 mmHg = 1.02 atm  (760 mmHg= 1 atm)
V= Volume of gas = volume of container = 49.8 L
n = number of moles = ?
T = Temperature of the gas = 26°C=(26+273)K= 299 K   (0°C = 273 K)
R= Value of gas constant = 0.0821 Latm\K mol
 
Thus the now the container contains 2.07 moles.