Determine the percent composition of each element in NH4Br
The Correct Answer and Explanation is:
To determine the percent composition of each element in NH₄Br (ammonium bromide), we first need the molar mass of the compound and the atomic masses of each element involved:
- N (Nitrogen) = 14.01 g/mol
- H (Hydrogen) = 1.008 g/mol × 4 = 4.032 g/mol
- Br (Bromine) = 79.90 g/mol
Now, calculate the molar mass of NH₄Br:Molar mass of NH₄Br=14.01+4.032+79.90=97.942 g/mol\text{Molar mass of NH₄Br} = 14.01 + 4.032 + 79.90 = 97.942 \, \text{g/mol}Molar mass of NH₄Br=14.01+4.032+79.90=97.942g/mol
Step 1: Percent composition of Nitrogen (N)
14.0197.942×100=14.30%\frac{14.01}{97.942} \times 100 = 14.30\%97.94214.01×100=14.30%
Step 2: Percent composition of Hydrogen (H)
4.03297.942×100=4.11%\frac{4.032}{97.942} \times 100 = 4.11\%97.9424.032×100=4.11%
Step 3: Percent composition of Bromine (Br)
79.9097.942×100=81.59%\frac{79.90}{97.942} \times 100 = 81.59\%97.94279.90×100=81.59%
Final Answer:
- Nitrogen: 14.30%
- Hydrogen: 4.11%
- Bromine: 81.59%
Explanation
Percent composition tells us how much by mass each element contributes to a compound. To find this, we start by determining the molar mass, which is the total mass of one mole of a compound. For NH₄Br, we calculate the molar mass by adding up the atomic masses of each atom in the compound: one nitrogen atom, four hydrogen atoms, and one bromine atom.
First, nitrogen has a molar mass of 14.01 grams per mole. Hydrogen has a molar mass of 1.008 grams per mole, and since there are four hydrogen atoms, their total mass is 4.032 grams per mole. Bromine is much heavier, with a mass of 79.90 grams per mole. The total molar mass of ammonium bromide becomes 97.942 grams per mole.
To find the percent composition, we divide the mass of each element by the total molar mass and multiply by 100 to get the percentage. For nitrogen, 14.01 divided by 97.942 and then multiplied by 100 gives 14.30 percent. Hydrogen’s total contribution is 4.032 grams, so its percent composition is 4.11 percent. Bromine, being the heaviest part, makes up the largest portion at 81.59 percent.
Knowing the percent composition is useful in chemistry for tasks like identifying unknown substances, determining empirical formulas, and preparing compounds with specific ratios. It gives a clear picture of how much of each element is present in a compound by mass.
