If 73.5 g of liquid Br2 and 330 mL of 1.18 M aqueous NaI are reacted stoichiometrically according to the balanced equation, how many grams of liquid Br2 remain? Round your answer to 3 significant figures.
2NaI(aq) + Br2(l) → 2NaBr(aq) + I2(s)
mols NaI = 0.330 x 1.18 = 0.389
How much Br2 will it use? Look at the coefficients in the balanced equation. It will need half of that; therefore, 0.389/2 = ? mols Br2 use. How many grams is that? g = moles Br2 used x molar mass.
75.3 g initially - g used = g remaining. Check all of my numbers. I rounded here and there.
To answer this question, we need to calculate the number of moles of Br2 present in the initial solution and the number of moles of Br2 reacted based on the stoichiometry of the balanced equation. Then we can subtract the moles of Br2 reacted from the initial moles to find the remaining moles of Br2. Finally, we can convert the remaining moles of Br2 to grams using the molar mass of Br2. Let's go step by step:
Step 1: Calculate the number of moles of Br2 present initially:
To do this, you need to use the given mass of Br2 and its molar mass. The molar mass of Br2 is approximately 159.808 g/mol. Use the formula:
Number of moles = mass / molar mass
Number of moles of Br2 = 73.5 g / 159.808 g/mol
Step 2: Calculate the number of moles of Br2 reacted:
According to the balanced equation, 1 mole of Br2 reacts with 2 moles of NaI. Therefore, the mole ratio between Br2 and NaI is 1:2. This means that for every 2 moles of NaI reacted, 1 mole of Br2 is reacted. So, the number of moles of Br2 reacted can be calculated as:
Number of moles of Br2 reacted = (Number of moles of NaI) / 2
To find the number of moles of NaI, we need to calculate it using the given volume and concentration. Concentration is given in moles per liter (M), so we need to convert the given volume from milliliters (mL) to liters (L).
Volume of NaI solution = 330 mL = 330/1000 L = 0.33 L
Number of moles of NaI = volume (L) x concentration (M)
Number of moles of NaI = 0.33 L x 1.18 M
Now, we can calculate the number of moles of Br2 reacted:
Number of moles of Br2 reacted = (0.33 L x 1.18 M) / 2
Step 3: Calculate the remaining moles of Br2:
To calculate the remaining moles of Br2, subtract the moles of Br2 reacted from the initial moles of Br2:
Remaining moles of Br2 = Number of moles of Br2 initially - Number of moles of Br2 reacted
Step 4: Convert the remaining moles of Br2 to grams:
Finally, we can convert the remaining moles of Br2 to grams by multiplying by the molar mass of Br2:
Mass of remaining Br2 = Remaining moles of Br2 x molar mass of Br2
Mass of remaining Br2 = (Remaining moles of Br2) x 159.808 g/mol
Let's calculate the answer using the given values:
Number of moles of Br2 = 73.5 g / 159.808 g/mol = 0.4599 mol (rounded to 4 decimal places)
Number of moles of NaI = 0.33 L x 1.18 M = 0.3894 mol (rounded to 4 decimal places)
Number of moles of Br2 reacted = (0.3894 mol) / 2 = 0.1947 mol (rounded to 4 decimal places)
Remaining moles of Br2 = 0.4599 mol - 0.1947 mol = 0.2652 mol (rounded to 4 decimal places)
Mass of remaining Br2 = 0.2652 mol x 159.808 g/mol = 42.390 g (rounded to 3 significant figures)
Therefore, 42.390 grams of liquid Br2 remains.