A student adds 0. 0030 mol of hcl to 100 ml of a 0. 10 m solution of a r2nh, a weak base. The ph of the solution is found to be
1 answer:
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The pink color in the solution fades. Some of the colored indicator ion converts to the colorless indicator molecule.
<h3>Explanation</h3>What's the initial color of the solution?
is a salt soluble in water.
dissociates into ions completely when dissolved.
.
The first test tube used to contain .
is a weak base that dissociates partially in water.
.
There's also an equilibrium between and
ions.
.
ions from
will shift the equilibrium between
and
to the right and reduce the amount of
in the solution.
The indicator equilibrium will shift to the right to produce more ions along with the colored indicator ions. The solution will show a pink color.
What's the color of the solution after adding NH₄Cl?
Adding will add to the concentration of
ions in the solution. Some of the
ions will combine with
ions to produce
.
The equilibrium between and
ions will shift to the left to produce more of both ions.
The indicator equilibrium will shift to the left as the concentration of increases. There will be less colored ions and more colorless molecules in the test tube. The pink color will fade.
Answer:
Sr(OH)₂ will be the limiting reagent.
Explanation:
First of all, you should know the following balanced chemical equation:
2 H₂CO₃ + 2 Sr(OH)₂ → 4 H₂O + Sr₂(CO₃)₂
The balanced equation is based on the Law of Conservation of Mass, which says that matter cannot be created or destroyed. Therefore, the number of each type of atom on each side of a chemical equation must be the same.
The limiting reagent is one that is consumed first in its entirety, determining the amount of product in the reaction. When the limiting reagent is finished, the chemical reaction will stop.
To determine the limiting reagent, it is possible to use the reaction stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction). By stoichiometry the following amounts in moles react:
- strontium hydroxide: 2 moles
- carbonic acid: 2 moles
Now, you know the following masses of the elements:
- Sr: 87.62 g/mole
- O: 16 g/mole
- H: 1 g/mole
So the molar mass of strontium hydroxide is:
Sr(OH)₂= 87.62 g/mole + 2*(16 g/mole + 1 g/mole)= 121.62 g/mole
You apply the following rule of three, if 121.62 grams of hydroxide are present in 1 mole, 12.5 grams in how many moles are they?
moles of hydroxide= 0.103 moles
On the other hand, you have 150 ml of 3.5 M carbonic acid. Since molarity is the concentration of a solution expressed in the number of moles dissolved per liter of solution, you can apply the following rule of three: if in 1 L there are 3.5 moles of carbonic acid, in 0.150 L (being 1 L = 1000 mL, 0.150 L = 150 mL) how many moles of acid are there?
moles of carbonic acid= 0.525 moles
Finally, to calculate the limiting reagent, you can use a simple rule of three as follows: if by stoichiometry 2 mole of strontium hydroxide reacts with , how much moles of carbonic acid will be needed if 0.103 moles of strontium hydroxide react?
moles of carbonic acid= 0.103 moles
But 0.525 moles are available. Since more moles are available than you need to react with 0.103 moles of strontium hydroxide, <u><em>Sr(OH)₂ will be the limiting reagent.</em></u>