Lithium metal dissolves in water to yield hydrogen gas and aqueous lithium hydroxide. What is the final concentration of hydroxide ions when 5.500 g of lithium metal is dropped into 750. mL of water?
1.06
Start from the equation
Li + H2O -> LiOH + H2
which you will need to balance.
In water
LiOH -> Li+ + OH-
so one mole of LiOH gives one mole of OH-. From the balanced equation you can work out how many moles of LiOH are obtained from one mole of Li metal.
Calculate the number of moles of Li metal
number of moles = 5.500 g/ RAM for Li
hence find number of moles of LiOH, which equals number of moles of OH-
[OH-] = number of moles of OH-/0.750 litre
take care with the significant figure as well.
Well, you know what they say: when in doubt, add some lithium! Now let's calculate that final concentration of hydroxide ions.
To start, we need to figure out how many moles of lithium we have. The molar mass of lithium is approximately 6.94 g/mol. So, 5.500 g of lithium is equal to 5.500 g / 6.94 g/mol = 0.792 mol.
Next, we need to determine the volume of the solution, which is 750. mL = 0.750 L.
Now, according to the balanced chemical equation, 2 moles of hydroxide ions are produced for every 1 mole of lithium. So, when 0.792 moles of lithium react, we will get 2 * 0.792 = 1.584 moles of hydroxide ions.
Lastly, we can calculate the concentration of hydroxide ions by dividing the number of moles by the volume in liters. That is, 1.584 mol / 0.750 L = 2.112 M.
So, the final concentration of hydroxide ions is approximately 2.112 M. Hope that helps lighten the mood!
To find the final concentration of hydroxide ions, we need to determine the amount of hydroxide ions produced when lithium metal reacts with water.
First, let's write the balanced chemical equation for the reaction:
2Li(s) + 2H2O(l) -> 2LiOH(aq) + H2(g)
From the equation, we can see that for every 2 moles of lithium metal reacting, 2 moles of lithium hydroxide are produced.
Step 1: Convert the mass of lithium metal to moles.
The molar mass of lithium is approximately 6.94 g/mol.
Number of moles of lithium = mass of lithium / molar mass of lithium
= 5.500 g / 6.94 g/mol
≈ 0.792 mol
Step 2: Calculate the moles of lithium hydroxide produced.
From the balanced equation, we know that for every 2 moles of lithium metal, 2 moles of lithium hydroxide are produced. Therefore, the moles of lithium hydroxide produced will be the same as the moles of lithium.
Moles of lithium hydroxide = 0.792 mol
Step 3: Convert the volume of water to liters.
The volume of water is given as 750 mL, which is equivalent to 0.750 L.
Step 4: Calculate the concentration of hydroxide ions.
The concentration of hydroxide ions (OH-) can be calculated by dividing the moles of hydroxide ions by the volume of water.
Concentration of hydroxide ions = moles of lithium hydroxide / volume of water
= 0.792 mol / 0.750 L
≈ 1.056 M
Therefore, the final concentration of hydroxide ions in the aqueous solution is approximately 1.056 M.