The molar ratio of carbon to hydrogen of a volatile liquid compound is 1:2. 0.12g of the liquid on evaporation at 6 s.t.p gave 32cm³ of vapour. The molecular formular of the liquid is (GMV=22.4dm³ C=12, H=1)
What is 6 stp
To find the molecular formula of the volatile liquid compound, we need to determine the number of moles of carbon and hydrogen present in the liquid from the given information.
1. Calculate the number of moles of carbon:
Given mass of the liquid = 0.12g
Molar mass of carbon (C) = 12 g/mol
Number of moles of carbon = Mass of carbon / Molar mass of carbon
= 0.12g / 12 g/mol
= 0.01 mol
2. Calculate the number of moles of hydrogen:
The molar ratio of carbon to hydrogen is 1:2. Therefore, there are twice as many moles of hydrogen as carbon.
Number of moles of hydrogen = 2 * Number of moles of carbon
= 2 * 0.01 mol
= 0.02 mol
3. Calculate the total number of moles:
Total number of moles = Moles of carbon + Moles of hydrogen
= 0.01 mol + 0.02 mol
= 0.03 mol
4. Convert the volume of the vapor to liters:
Given volume of vapor = 32 cm³ = 32 mL = 32/1000 L
= 0.032 L
5. Calculate the molar volume of the vapor at STP:
One mole of any gas occupies 22.4 dm³ (or 22.4 L) at standard temperature and pressure (STP).
Molar volume of the vapor at STP = 22.4 dm³ = 22.4 L
6. Determine the number of moles of the vapor:
Number of moles of the vapor = Volume of the vapor / Molar volume of the vapor at STP
= 0.032 L / 22.4 L/mol
= 0.00143 mol
7. Find the empirical formula:
The empirical formula represents the simplest whole number ratio of the elements present in a compound.
To find the empirical formula, divide the number of moles of each element by the smallest number of moles obtained.
The ratio of moles of carbon to hydrogen is 0.01 mol : 0.02 mol.
Simplifying this ratio by dividing by 0.01, we get a ratio of 1 : 2.
Therefore, the empirical formula is CH₂.
8. Calculate the empirical formula mass:
Empirical formula mass = (Mass of carbon atoms) + (Mass of hydrogen atoms)
= (Atomic mass of carbon) + 2 * (Atomic mass of hydrogen)
= 12 g/mol + 2 * 1 g/mol
= 14 g/mol
9. Determine the molecular formula:
The given molecular volume is 0.03 mol, and the empirical formula mass is 14 g/mol.
Molecular formula = (Empirical formula) * (n), where n = Molecular formula mass / Empirical formula mass
Molecular formula = CH₂ * (0.03 mol / 14 g/mol)
= CH₂ * (0.00214 mol/g)
Simplifying further, we can say that the molecular formula is approximately 0.00214 moles per gram of CH₂, which is not a whole number. Hence, we cannot determine the specific molecular formula with the given information.
To determine the molecular formula of the liquid compound, we need to follow certain steps:
Step 1: Calculate the number of moles of hydrogen gas produced.
- Gas volume at STP (standard temperature and pressure) is given as 32 cm³.
- Convert the volume from cm³ to dm³: 32 cm³ = 32/1000 dm³ = 0.032 dm³.
- Use the molar volume of gas at STP: 0.032 dm³ x (1 mol/22.4 dm³) = 0.00143 mol (rounded to 5 decimal places).
Step 2: Calculate the number of moles of carbon in the liquid.
- From the given information, the molar ratio of carbon to hydrogen is 1:2.
- Since the molar ratio is in a 1:2 ratio and we know the number of moles of hydrogen is 0.00143 mol, the number of moles of carbon would be half of that.
- 0.00143 mol / 2 = 0.000715 mol (rounded to 6 decimal places).
Step 3: Calculate the mass of carbon and hydrogen in the liquid.
- The molar mass of carbon (C) is 12 g/mol, and the molar mass of hydrogen (H) is 1 g/mol.
- Mass of carbon = 0.000715 mol x 12 g/mol = 0.00858 g (rounded to 5 decimal places).
- Mass of hydrogen = 0.00143 mol x 1 g/mol = 0.00143 g (rounded to 5 decimal places).
Step 4: Determine the empirical formula of the liquid compound.
- The empirical formula represents the simplest mole ratio of elements in a compound.
- To find the empirical formula, we need to divide the number of moles of each element by the smallest number of moles.
- In this case, the smallest number of moles is 0.000715 mol.
- For carbon, 0.00858 g / 12 g/mol = 0.000715 mol.
- For hydrogen, 0.00143 g / 1 g/mol = 0.00143 mol.
- Dividing both values by 0.000715 mol gives us a 1:2 ratio, which is consistent with the original molar ratio provided in the question.
Step 5: Determine the molecular formula of the compound.
- To find the molecular formula, we need to know the molar mass of the compound.
- From the empirical formula, we can calculate the empirical formula mass by multiplying the atomic masses of each element by their respective subscripts.
- The empirical formula mass is given by: (1 x atomic mass of C) + (2 x atomic mass of H).
- Empirical formula mass = (1 x 12 g/mol) + (2 x 1 g/mol) = 14 g/mol.
Step 6: Calculate the ratio of the molecular mass to the empirical formula mass.
- The given molecular volume of the compound is 22.4 dm³.
- We also know that the molar volume of gas at STP (GMV) is 22.4 dm³/mol.
- The ratio of the molecular mass to the empirical formula mass is calculated by dividing the given molecular volume by the molar volume of gas at STP.
- Ratio = 22.4 dm³ / 22.4 dm³/mol = 1 (rounded to 1 decimal place).
Step 7: Calculate the molecular formula.
- Since the ratio of the molecular mass to the empirical formula mass is 1, the empirical formula is also the molecular formula.
- Therefore, the molecular formula of the liquid compound is CH₂.