Answer:
C3H8
Explanation:
Step 1:
Relevant details from the question are noted below:
Mass of the alkane is 1.17g
Volume (V) = 674 mL
Temperature (T) = 28°C
Pressure (P) = 741 mmHg.
Gas constant (R) = 0.08206 atm.L/Kmol
Step 2:
Convert to the appropriate units.
For Volume:
1000mL = 1L
So, 674mL = 674/1000 = 0.674L
For Temperature:
Temperature in Kelvin = Temperature in Celsius + 273
Temperature in Celsius = 28°C
Temperature in Kelvin = 28°C + 273 = 301K
For Pressure:
760mmHg = 1atm
So, 741 mmHg = 741/760 = 0.975atm
Step 3:
Calculate the moles of the alkane.
The moles of the alkane can be found using the ideal gas equation, presented below:
Volume (V) = 0.674L
Temperature (T) = 301K
Pressure (P) = 0.975atm
Gas constant (R) = 0.08206 atm.L/Kmol
Number of moles (n) =?
PV = nRT
n = PV /RT
n = (0.975 x 0.674)/(0.08206x301)
n = 0.0266 moles
Step 4:
Calculate the alkane’s molar mass.
Mass of alkane = 1.17g
Number of moles = 0.0266moles
Molar Mass =?
Number of moles = Mass/Molar Mass
Molar Mass = Mass/Number of moles
Molar Mass of alkane = 1.17/0.0266 = 44g/mol
Step 5:
Determine the molecular formula of the alkane.
This is based on:
The general formula for alkanes is CnH2n+2
To find the molecular formula, we start with n = 1, 2, 3, etc., until we find the molar mass of 44.
When n = 1
CnH2n+2 = CH4 = 12 + (4x1) = 16g/mol
When n = 2
CnH2n+2 = C2H6 = (12x2) + (6x1) = 30g/mol
When n = 3
CnH2n+2 = C3H8 = (12x3) + (8x1) = 44g/mol
It can be observed that for n equal to 3, the molar mass is 44g/mol.
Thus, the molecular formula of the alkane is C3H8.
