Determining a formula of a hydrate

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In summary: One of the most common factors is the molarity, which is defined as the number of moles of a substance per liter of solution. For most titrations, the molarity of the acid/base is 1.0 (i.e. 1 mole of acid per 1 mole of base).
  • #1
~angel~
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Barium hydroxide froms several hydrates. A specimen of barium hydroxide, suspected of being a hydrate, was prepared and analysed as follows to determine its formula.

3.632 g of the compound was dissolved in water to give 250.0mL of solution. 25.00 mL of this solution was titrated with 0.0987 M of HCl, using methyl-orange as indicator. Precise titrations of 23.34, 23.26 and 23.29 mL of HCl were obtained. Determine the formula of the hydrate.

I tried writing a balanced equation for the reaction, but I can't seem to balance it.

Also, I'm not exactly sure how to approach this problem so any help would be greatly appreciated.

Thanks.
 
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  • #2
~angel~ said:
Barium hydroxide froms several hydrates. A specimen of barium hydroxide, suspected of being a hydrate, was prepared and analysed as follows to determine its formula.

3.632 g of the compound was dissolved in water to give 250.0mL of solution. 25.00 mL of this solution was titrated with 0.0987 M of HCl, using methyl-orange as indicator. Precise titrations of 23.34, 23.26 and 23.29 mL of HCl were obtained. Determine the formula of the hydrate.

I tried writing a balanced equation for the reaction, but I can't seem to balance it.

Also, I'm not exactly sure how to approach this problem so any help would be greatly appreciated.

Thanks.
A good start to most titration questions is to find the number of moles of the known acid/base that was used and then find the number of moles used for the acid. Then find how many moles there are in the solution of the acid/base that you are trying to work out.

The Bob (2004 ©)
 
  • #3
I know what you mean but I can't seem to balance the equation.

I thought it was BaOH + HCl --> BaCl2 + H2O

If that is right, how do you balance is because it seems to be one of those equations where no matter what number you put in front, it is different on the other side.

Thanks
 
  • #4
Barium has 2+ for its charge. Hydroxide is a -1 ion.
 
  • #5
Well that's explains it. Thanks.

I haven't really encountered a problem like this before. I have found the number of moles for each substance. Ba(OH)2 has 1/2 the moles of HCl. Is this for 25.0mL?

How exactly can I determine the formula from what I've got?

Thanks.
 
  • #6
I'm not sure if this will be of specific help here, but still:

In titrations, a more fundamental quantity is gram equivalents (or milliequivalents). If A and B are titrated with each other, then gram equivalents of A = gram equivalents of B. To convert from moles to gram equivalents and vice versa, you need to multiply and divide by a factor. As you can see using simple examples, moles of A and B are not necessarily equal in titrations and there's usually a factor involved.
 

1. What is a hydrate?

A hydrate is a compound that contains water molecules bound within its crystal structure. These water molecules are known as "water of hydration" and are essential for the compound's stability and physical properties.

2. Why is it important to determine the formula of a hydrate?

Determining the formula of a hydrate is important because it allows us to understand the chemical composition and structure of the compound. This information is crucial for various applications, such as in industries that use hydrates as catalysts or in medicine where hydrates are used as active ingredients.

3. What is the process for determining the formula of a hydrate?

The process involves heating the hydrate to remove the water molecules and then measuring the mass of the remaining compound. The mass of the water lost is also measured. Using these values, we can calculate the ratio of the water molecules to the anhydrous compound and determine the formula of the hydrate.

4. Are there any safety precautions to consider when determining the formula of a hydrate?

Yes, it is important to handle the hydrate with caution and use proper protective equipment as some hydrates can be toxic or corrosive. The heating process should also be done carefully to avoid any accidents or burns.

5. Can the formula of a hydrate change under certain conditions?

Yes, the formula of a hydrate can change under certain conditions, such as changes in temperature or pressure. This can cause the water molecules to be released or absorbed, altering the composition of the compound. This is why it is important to specify the conditions under which the formula was determined.

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