Types of formula

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  • Created by: racheon
  • Created on: 04-02-14 15:48
Define emperical formula.
The simplest whole-number ratio of atoms of each element present in a compound.
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Why does NaCl have this formula?
Because there is always 1 Na+ ion for every Cl- ion.
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What type of compound of NaCl?
An ionic compound.
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Emperical formula is used for ionic compounds and what other type of compound?
Covalent.
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Analysis showed that 0.6075g of magnesium combines with 3.995g of bromine to form a compound [Ar: Mg = 24.3, Br = 79.9]. Work out the emperical formula (3 steps).
1. Find the molar ratio of atoms: Mg - 0.6075/24.3 = 0.025. Br - 3.995/79.9 = 0.05. 2. Divide by smallest number: 1:2. 3. Empirical formula is MgBr2.
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Analysis of a compound showed the following percentage composition by mass: Na=79.19%, O=25.81% [Ar: Na=23, O=16]. Find the empirical formula.
Find the molar ratio of atoms: Na - 79.19/23 = 3.443. O - 25.81/16 = 1.613. Divide by smallest number: 2:1. Empirical formula is Na2O.
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Define molecular formula.
The actual number of atoms of each element in a molecule.
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Butane has 4C atoms and 10H atoms. What is it's molecular formula and empirical formula?
Molecular formula = C4H10. Empirical formula = C2H5.
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A compound has an empirical formula of CH2 and a relative molecular mass of 56. What is its molecular formula?
Empirical formula mass = 12 + (1x2) = 14. Number of CH2 units in a molecule = 56/14 = 4. Molecular formula = (4xCH2) = C4H8.
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What is the equation for working out moles?
amount (n) = mass (m)/molar mass (M).
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Other cards in this set

Card 2

Front

Why does NaCl have this formula?

Back

Because there is always 1 Na+ ion for every Cl- ion.

Card 3

Front

What type of compound of NaCl?

Back

Preview of the front of card 3

Card 4

Front

Emperical formula is used for ionic compounds and what other type of compound?

Back

Preview of the front of card 4

Card 5

Front

Analysis showed that 0.6075g of magnesium combines with 3.995g of bromine to form a compound [Ar: Mg = 24.3, Br = 79.9]. Work out the emperical formula (3 steps).

Back

Preview of the front of card 5
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