Advertisements
Advertisements
Question
A gaseous hydrocarbon contains 82.76% of carbon. Given that its vapor density is 29, find its molecular formula. [C = 12, H = 11]
Advertisements
Solution
| Element | Percentage | Molecules | Simple ratio | Ration | Simple whole ratio |
| Carbon | 82.76 | `82.76/12` = 6.9 | `6.89/6.89` = 1 | `6.9/6.9` = 1 | 2 |
| Hydrogen | 17.24 | `17.24/1` = 17.24 | `17.24/6.89` = 2.5 | `17.24/6.9` = 2.5 | 5 |
Empirical formula = C2H5
Empirical formula mass = (12 × 2) + (1 × 5)
= 24 + 5
= 29
Vapour density = 29 ...(Given)
Molecular weight = 2 × Vapour density
Molecular weight = 2 × 29
= 58 gm
Molecular formula mass = n × Empirical formula mass
⇒ n = `"Molecular formula mass"/"Empirical formula mass"`
= `58/29`
= 2
Molecular formula = n × Empirical formula
= 2 × C2H5
= C4H10
RELATED QUESTIONS
Identify the term or substance based on the descriptions given below:
The property by virtue of which the compound has the same molecular formula but different structural formulae.
Give the empirical formula of C6H6.
Give the empirical formula of C2H2
A compound of lead has following percentage composition, Pb = 90.66%, O = 9.34%. Calculate empirical formula of a compound. [Pb = 207, O = 16]
A compound contains 87.5% by mass of nitrogen and 12.5% by mass of hydrogen. Determine the empirical formula of this compound.
The compound A has the following percentage composition by mass: C =26.7%, O = 71.1%, H = 2.2%.
Determine the empirical formula of A.(Answer to one decimal place) (H=1,C=12,O=16)
The percentage composition of sodium phosphate, as determined by analysis is : 42.1% Na, 18.9% P, 39% of O. Find the empirical formula of the compound.
[H =1, N =14, Na = 23, P = 31, Cl = 35.5, Pt = 195]
Determine the empirical formula of a compound containing 47.9‰ K, 5.5‰ beryllium and 46.6‰ fluorine by mass.
In a compound of magnesium (Mg = 24) and nitrogen (N = 14), 18 g of magnesium combines with 7g of nitrogen.
Deduce the simplest formula by answering the following questions:
- How many gram-atoms of magnesium are equal to 18g?
- How many gram-atoms of nitrogen are equal to 7g of nitrogen?
- Calculate the simple ratio of gram-atoms of magnesium to gram-atoms of nitrogen and hence the simplest formula of the compound formed.
A compound has the following percentage composition by mass: carbon 14.4%, hydrogen 1.2% and chlorine 84.5%. By what type of reaction could this compound be obtained from ethylene?
