# Chemistry-Finding concentrations of two compounds

• taxidriverhk
In summary: So from concentration of sulfate in the solution that is not in the precipitate, you can find the initial concentration of sodium sulfate.In summary, when given a balanced chemical reaction and information about the products and reactants, we can use the law of conservation of mass and the concept of spectator ions to find the initial concentrations of each reactant. In this specific case, by looking at the number of moles of NO3- and using the chemical equation, we can find the initial concentration of Ba(NO3)2. The excess sulfate ion in the final solution can also be used to find the initial concentration of Na2SO4.
taxidriverhk

## Homework Statement

Given balanced chemical reaction:
Ba(NO3)2 (aq) + Na2SO4 (aq) → BaSO4 (s) + 2NaNO3 (aq)

Suppose 200 mL of Ba(NO3)2 and 200 mL of Na2SO4 of unknown concentrations are mixed together and forms the reaction above. Then, there are 0.0120 M of NaNO3 produced, and 0.0004 M of excess sulfate ion. Find the initial concentration of each reactant.

## Homework Equations

Molarity = number of moles/volume of solvent

## The Attempt at a Solution

I led x be the concentration of Ba(NO3)2
and y be the concentration of Na2SO4
Then I used the law of conservation of mass to find the total mass of reactants and products, then wrote the equation below
5.6x + 28.4y = 0
But I am now not sure what to do next, do I need to find the volume of the solution produced or to do something else?
Please give me some hints or concepts so that I can figure it out, I will be extremely appreciated...

It can be solved in many ways, but the simplest approach is to look for things that have not changed. How many moles of NO3- in the final solution? How is this number related to the initial number of moles of Ba(NO3)2?

Borek said:
It can be solved in many ways, but the simplest approach is to look for things that have not changed. How many moles of NO3- in the final solution? How is this number related to the initial number of moles of Ba(NO3)2?

I think I may get some ideas from what you asked
I now try to write out the net ionic equation for the reaction below
Ba2+ + 2NO3- + 2Na+ + SO42- → BaSO4 + 2Na+ + 2NO3-
And I find out that NO3- and Na+ are spectator ions, that means their concentrations did not change right?
But the problem is I don't know how to find the final concentrations of each ion from the given concentration of NaNO3 which is 0.0120M, should I divide it half and half, or is there some other ways? Please advise..

taxidriverhk said:
And I find out that NO3- and Na+ are spectator ions, that means their concentrations did not change right?

Concentration changes, but not because of teh reaction - you mix two solutions, so they are diluted.

But the problem is I don't know how to find the final concentrations of each ion from the given concentration of NaNO3 which is 0.0120M, should I divide it half and half, or is there some other ways? Please advise..

If concentration of NaNO3 is 0.0120M, concentrations of both Na+ and NO3- are also 0.0120M. This is not always the case, but here NaNO3 dissociates into 1+1 ions.

So the final concentration of each ion is below
Ba2+ = 0 M
SO42- = 0.0004 M
Na+ = 0.0120 M
NO3- = 0.0120 M
is it right?
If they are right, then I will be able to find the initial concentration of Ba(NO3)2 by first finding the number of moles of NaNO3, and use the chemical equation to convert it to the number of moles of Ba(NO3)2, and finally divide it by 0.2 L to find out the initial concentration, did I think it right?
But how about the initial concentration of another compound? I got confused by the excess 0.0004M sulfate acid

You are right about initial concentration of Ba(NO3)2.

Part of the sulfate is in the precipitate (this part you can easily calculate from known initial concentration of barium), part of the sulfate is still in the solution. Sum of these was present in the initial solution of sodium sulfate.

## 1. How do you calculate the concentration of a compound?

The concentration of a compound can be calculated by dividing the amount of the compound by the total volume of the solution. This is represented by the formula: concentration (g/L) = mass (g) / volume (L).

## 2. What is the difference between molarity and molality?

Molarity refers to the concentration of a solution in terms of moles of solute per liter of solution, while molality refers to the concentration of a solution in terms of moles of solute per kilogram of solvent. Molarity takes into account the volume of the solution, while molality takes into account the mass of the solvent.

## 3. How do you find the concentration of two compounds in a mixture?

To find the concentration of two compounds in a mixture, you can use the formula: concentration of compound A x volume of solution = concentration of compound B x volume of solution. This is known as the dilution equation.

## 4. What is the difference between concentration and density?

Concentration refers to the amount of a substance in a given volume of solution, while density refers to the mass per unit volume of a substance. Concentration is typically measured in units of moles per liter, while density is measured in units of grams per cubic centimeter.

## 5. How do you determine the concentration of a compound in a titration?

In a titration, the concentration of a compound can be determined by adding a known volume of a solution with a known concentration (known as the titrant) to a measured volume of a solution with an unknown concentration (known as the analyte) until the reaction is complete. By knowing the volume and concentration of the titrant, the concentration of the analyte can be calculated using the titration formula.

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