Determine the number of bromide ions in solution when 4.23 g of magnesium bromide and 1.21 g of potassium bromide are dissolved in 120mL of water.
Please explain not sure how to even start this problem, thanks!
Convert 4.23 g MgBr2 to moles and multiply that by 2 to obtain moles Br^- from MgBr2. moles = grams/molar mass.
Convert 1.21 g KBr the same way. Add the moles Br^- together to obtain total moles, then remember that 1 mole of Br^- ions will contain 6.022E23 ions.
4.23g MgBr2 Moles= grams/molar mass
4.23/184.113 = 0.023 moles
1.21g KBr Moles= grams/molar mass
1.21/119.002 = 0.033
and than what? I add those two #'s together? 0.033 + 0.023 = 0.033
and I don't know what you mean by 1 mole of Br- ions will contain 6.022e23 ions where did you get that info?
Thanks!
To determine the number of bromide ions in solution, you need to calculate the number of moles of magnesium bromide and potassium bromide separately, and then use their chemical formulas to find the number of bromide ions.
1. Calculate the number of moles of magnesium bromide:
- Determine the molar mass of magnesium bromide (MgBr₂). The atomic mass of magnesium (Mg) is 24.31 g/mol, and the atomic mass of bromine (Br) is 79.90 g/mol.
Molar mass of MgBr₂ = (2 × atomic mass of Br) + atomic mass of Mg
= (2 × 79.90 g/mol) + 24.31 g/mol
= 159.8 g/mol + 24.31 g/mol
= 184.11 g/mol
- Use the formula: moles = mass / molar mass
Moles of magnesium bromide = 4.23 g / 184.11 g/mol
2. Calculate the number of moles of potassium bromide:
- Determine the molar mass of potassium bromide (KBr). The atomic mass of potassium (K) is 39.10 g/mol, and the atomic mass of bromine (Br) is 79.90 g/mol.
Molar mass of KBr = atomic mass of Br + atomic mass of K
= 79.90 g/mol + 39.10 g/mol
= 119.0 g/mol
- Use the formula: moles = mass / molar mass
Moles of potassium bromide = 1.21 g / 119.0 g/mol
3. Find the number of bromide ions:
- The magnesium bromide compound has a 1:2 ratio of magnesium ions (Mg²⁺) to bromide ions (Br⁻). So, each formula unit of magnesium bromide contains two bromide ions.
- Multiply the moles of magnesium bromide by 2 to find the moles of bromide ions.
Moles of bromide ions from magnesium bromide = 2 × Moles of magnesium bromide
- The potassium bromide compound has a 1:1 ratio of potassium ions (K⁺) to bromide ions (Br⁻). So, each formula unit of potassium bromide contains one bromide ion.
- Multiply the moles of potassium bromide by 1 to find the moles of bromide ions.
Moles of bromide ions from potassium bromide = 1 × Moles of potassium bromide
4. Add the moles of bromide ions from both compounds to find the total moles of bromide ions in solution.
Total moles of bromide ions in solution = Moles of bromide ions from magnesium bromide + Moles of bromide ions from potassium bromide
5. Convert the moles of bromide ions to the number of bromide ions using Avogadro's number.
Number of bromide ions = Total moles of bromide ions in solution × Avogadro's number
By following these steps, you will be able to determine the number of bromide ions in solution.
To determine the number of bromide ions in solution, you need to calculate the amount of bromide ions provided by each compound and then add them together.
To start, you need to know the molecular formula of each compound.
- Magnesium bromide has the formula MgBr2, indicating that each molecule contains two bromide ions (Br-).
- Potassium bromide has the formula KBr, meaning that each molecule contains one bromide ion (Br-).
Next, you need to convert the given masses of magnesium bromide and potassium bromide into moles. To do this, use the molar mass of each compound.
- The molar mass of magnesium bromide (MgBr2) is calculated as follows:
Molar mass of MgBr2 = (molar mass of Mg) + 2 × (molar mass of Br)
= (24.31 g/mol) + 2 × (79.90 g/mol)
= 24.31 g/mol + 159.80 g/mol
= 184.11 g/mol
- The molar mass of potassium bromide (KBr) is calculated as follows:
Molar mass of KBr = (molar mass of K) + (molar mass of Br)
= (39.10 g/mol) + (79.90 g/mol)
= 119.00 g/mol
Now, calculate the number of moles of each compound:
- Moles of magnesium bromide = mass / molar mass
= 4.23 g / 184.11 g/mol
= 0.023 mol (approx.)
- Moles of potassium bromide = mass / molar mass
= 1.21 g / 119.00 g/mol
= 0.0102 mol (approx.)
Next, calculate the number of bromide ions provided by each compound:
- Magnesium bromide provides 2 bromide ions per mole. Therefore, the number of bromide ions contributed by magnesium bromide is:
Number of bromide ions from magnesium bromide = moles of magnesium bromide × 2
= 0.023 mol × 2
= 0.046 mol (approx.)
- Potassium bromide provides 1 bromide ion per mole. Therefore, the number of bromide ions contributed by potassium bromide is:
Number of bromide ions from potassium bromide = moles of potassium bromide × 1
= 0.0102 mol × 1
= 0.0102 mol (approx.)
Now, add the number of bromide ions from each compound:
Total number of bromide ions = number of bromide ions from magnesium bromide + number of bromide ions from potassium bromide
= 0.046 mol + 0.0102 mol
= 0.0562 mol (approx.)
Finally, convert the number of bromide ions to the desired units using Avogadro's number. Since 1 mole of any compound contains 6.022 × 10^23 particles (Avogadro's number):
Number of bromide ions in solution = Total number of bromide ions × Avogadro's number
= 0.0562 mol × 6.022 × 10^23 ions/mol
≈ 3.385 × 10^22 bromide ions