A sample of compound containing boron and hydrogen contains 6.444 g of B and 1.803 g of H. The molar mass of the compound is about 30 g. What is its empirical and molecular formula?...thank you for sharing your knowledge...

1. convert the masses to the mole using the molar mass;

n(B) = m/Mr = 6.444g/10gmol-1 = 0.6444mol

n(H) = m/Mr = 1.803g/1gmol-1 = 1.803mol

divide the moles by the smallest mole;

0.6444/0.6444 = 1 B

1.803/0.6444 = 2.79 H

Use the whole number as we are to find the empirical formula so 2.79 becomes 3.

so the compound contains 1mol of B and 3 mol of H
i.e. BH3

z = Mr/x where x is the molar mass of the empirical formula and z is the mole in whole number;
B = 10g/mol
H = 1g/mol x 3 = 3g/mol

Mr(BH3) = 13g/mol

z = 2.307 = 2

Molecular formula = z(BH3) = 2(BH3) = B2H6

***Note that i used the whole number molar masses and i end up with decimals which i rounded them off to the whole number. Try use the molar mass up to 2 sig figures from the periodic table which will help you get the whole number figures***

hope that helps

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To determine the empirical formula of a compound, we need to find the simplest whole number ratio of the elements present. To do this, we can follow these steps:

Step 1: Determine the moles of each element:
- Moles of boron (B) = mass of B / molar mass of B = 6.444 g / 10.81 g/mol = 0.595 mol
- Moles of hydrogen (H) = mass of H / molar mass of H = 1.803 g / 1.008 g/mol = 1.788 mol

Step 2: Find the mole ratio of the elements:
- Divide the moles of each element by the smallest number of moles (in this case, 0.595 mol for B):
- B: 0.595 mol / 0.595 mol = 1
- H: 1.788 mol / 0.595 mol = 3

Step 3: Convert the mole ratios to the simplest whole number ratio by dividing each subscript by the smallest one:
- The empirical formula is thus B1H3.

To determine the molecular formula, we need to know the molar mass of the compound. It is given as 30 g/mol.

Step 4: Calculate the empirical formula mass:
- Empirical formula mass = (atomic mass of B × number of B atoms) + (atomic mass of H × number of H atoms)
= (10.81 g/mol × 1) + (1.008 g/mol × 3) = 10.81 g/mol + 3.024 g/mol = 13.834 g/mol

Step 5: Divide the molar mass of the compound by the empirical formula mass to find the multiple:
- Multiple = molar mass of compound / empirical formula mass = 30 g/mol / 13.834 g/mol ≈ 2.17

Step 6: Multiply the subscripts in the empirical formula by the multiple:
- Molecular formula = (subscript of B in empirical formula) × (multiple) + (subscript of H in empirical formula) × (multiple)
= (1 × 2.17)B + (3 × 2.17)H
= 2.17B2.17H6.51

So, the empirical formula is B1H3, and the molecular formula is approximately B2H7.

To determine the empirical formula, we need to find the ratio of boron to hydrogen in the compound.

1. Calculate the moles of boron (B) and hydrogen (H) using their masses and molar masses:
- Moles of B = mass of B / molar mass of B
- Moles of H = mass of H / molar mass of H

Given the masses:
Mass of B = 6.444 g
Mass of H = 1.803 g

Given the molar masses:
Molar mass of B = 10.81 g/mol
Molar mass of H = 1.01 g/mol

Calculating the moles:
Moles of B = 6.444 g / 10.81 g/mol = 0.596 mol B
Moles of H = 1.803 g / 1.01 g/mol = 1.786 mol H

2. Find the simplest whole-number ratio of the moles of elements:
Divide the number of moles by the smallest number of moles obtained.

Dividing by 0.596 (the smallest number of moles), we get:
Moles of B = 0.596 / 0.596 ≈ 1 mol B
Moles of H = 1.786 / 0.596 ≈ 3 mol H

The ratio is approximately 1 : 3, so the empirical formula is BH3.

To determine the molecular formula, we need to know the molecular mass of the compound. Given that it is about 30 g, we need to compare the empirical formula mass to the molecular mass.

3. Calculate the empirical formula mass:
The empirical formula mass can be found by adding up the atomic masses in the empirical formula.

Atomic mass of B = 10.81 g/mol
Atomic mass of H = 1.01 g/mol

Empirical formula mass = (1 × 10.81 g/mol) + (3 × 1.01 g/mol) = 13.83 g/mol

4. Find the number of empirical formula units in one molecule:
Divide the molecular mass by the empirical formula mass.

Molecular mass = 30 g/mol
Number of empirical formula units = 30 g/mol / 13.83 g/mol ≈ 2

The molecular formula is then twice the empirical formula: (BH3)2.