Advertisements
Advertisements
Question
A compound of lead has following percentage composition, Pb = 90.66%, O = 9.34%. Calculate empirical formula of a compound. [Pb = 207, O = 16]
Advertisements
Solution
Empirical formula of a compound:
| Element | Atomic mass |
Percentage | Relative number of | Simplest mole ratio | Whole number ratio |
| Pb | 207 | 90.66 | 90.66/207 = 0.44 | 0.44/0.44 = 1 | 1 x 3 = 3 |
| O | 16 | 9.34 | 9.34/16 = 0.58 | 0.58/0.44 = 1.32 | 1.32 x 3 = 3.96 = 4 |
Since the mole ratio for oxygen is fractional so we multiply the whole ratio by 3 to make i t a whole number.
So, the empirical formula of the compound is Pb3O4.
APPEARS IN
RELATED QUESTIONS
A compound of X and Y has the empirical formula XY2. Its vapor density is equal to its empirical formula weight. Determine its molecular formula.
A gaseous hydrocarbon contains 82.76% of carbon. Given that its vapor density is 29, find its molecular formula. [C = 12, H = 11]
Consider the following reaction and based on the reaction answer the questions that follow:
Calculate:
1) the quantity in moles of (NH4)2Cr2O7 if 63gm of(NH4)2Cr2O7 is heated.
2) the quantity in moles of nitrogen formed.
3) the volume in liters or dm3 of N2 evolved at S.T.P.
4) the mass in grams of Cr2O3 formed at the same time
(Atomic masses: H=1, Cr= 52, N=14]
Give the empirical formula of: C6H12O6
Give the empirical formula of C2H2
Give the empirical formula of CH3COOH
Calculate the empirical formula of the compound having 37.6% sodium, 23.1% silicon and 39.3% oxygen.(Answer correct to two decimal places) (O = 16, Na = 23, Si = 28)
Calculate the percentage of water of crystallization in CuSO4. 5H2O
(H = 1, O = 16, S = 32, Cu = 64)
A compound of X and Y has the empirical formula XY2. Its vapour density is equal to its empirical formula weight. Determine its molecular formula.
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.
