Test Yourself 3.3:
1. What is meant by empirical formula and molecular formula?
2. Caffeine, C8H10N4O2 is a natural stimulant found in coffee, tea and cocoa. What is the empirical formula of caffeine?
3. Calcium carbonate and sodium fluoride are two compounds found in toothpaste. Write the chemical formulae of both compounds.
4. A sample of 5.04 g of oxide for phosphorus contains 2.48 g of phosphorus.
[Relative atomic mass: O = 16, F = 31]
(a) If the relative molecular mass of the oxide is 126, determine its empirical formula and molecular formula.
(b) Name the oxide of the phosphorus
Answer:
1. Empirical formula is the formula that shows the simplest ratio of the number of atoms of each element in a substance.
Molecular formula is the formula that shows the actual number of atoms of each element in a molecule of a substance.
2. C4H5N2O
3. CaCO3; NaF
4. (a) Molecular formula P2O4; Empirical formula PO2
(b) Diphosphorus tetraoxide
1. What is meant by empirical formula and molecular formula?
2. Caffeine, C8H10N4O2 is a natural stimulant found in coffee, tea and cocoa. What is the empirical formula of caffeine?
3. Calcium carbonate and sodium fluoride are two compounds found in toothpaste. Write the chemical formulae of both compounds.
4. A sample of 5.04 g of oxide for phosphorus contains 2.48 g of phosphorus.
[Relative atomic mass: O = 16, F = 31]
(a) If the relative molecular mass of the oxide is 126, determine its empirical formula and molecular formula.
(b) Name the oxide of the phosphorus
Answer:
1. Empirical formula is the formula that shows the simplest ratio of the number of atoms of each element in a substance.
Molecular formula is the formula that shows the actual number of atoms of each element in a molecule of a substance.
2. C4H5N2O
3. CaCO3; NaF
4. (a) Molecular formula P2O4; Empirical formula PO2
(b) Diphosphorus tetraoxide