Finding pH Values for Acids and Bases Without Experiments

In summary, the conversation revolved around a student seeking help with placing acids and bases on a pH scale for an assignment. They were struggling to understand the relationship between [H+] and pH, but after finding a helpful website and working through some problems, they were able to figure it out. A link to a helpful website was also shared.
  • #1
AngelShare
208
0
I have to place two acids and two bases from a previous assignment on a pH scale using the information I acquired during that particular experiment. The problem is, I couldn't get all the materials I needed so I didn't get to do the assignment. I've been able to figure out what vinegar's pH is but I can't seem to figure out any others. Does anyone know of any sites I could use?

The things I can place are as follows:

Hydrogen peroxide
Isopropyl alcohol
Saline solution
Pepto-Bismol
Tonic water
 
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  • #2
Ah, I'm completely lost...:bugeye:

What is the relationship between [H+] and pH?

pH = -log [H+]

H3O+

I'm trying, desperately, to grasp something but my mind is blank. I'm not comprehending anything here...help...:cry:
 
  • #3
AngelShare said:
Ah, I'm completely lost...:bugeye:

What is the relationship between [H+] and pH?

pH = -log [H+]

H3O+

I'm trying, desperately, to grasp something but my mind is blank. I'm not comprehending anything here...help...:cry:

You've given the relationship pH = -log [H+].

In this equation, [H+] is the concentration of the hydorgen ion in the solution. So, if you take the negative log of the hydrogen ion concentration (to the base 10), you get the pH.

Do you understand now?
 
  • #4
Yes, I found another site that explained it better, worked through a couple of problems, and figured it out.:smile:
 
  • #6
Ah, good site Borek, thanks!:biggrin:
 

1. How can I find the pH value of an acid or base without conducting experiments?

There are a few methods you can use to estimate the pH value of an acid or base without conducting experiments. One method is by using the Henderson-Hasselbalch equation, which involves using the acid dissociation constant (pKa) of the acid or base and the concentration of the solution. Another method is by using litmus paper or pH testing strips, which change color in the presence of acids or bases and can give a rough estimate of the pH value. Additionally, there are online pH calculators that use mathematical equations to estimate pH values based on the concentration and properties of the acid or base.

2. Can I use indicators to determine the pH value of an acid or base without experiments?

Indicators, such as litmus paper or pH testing strips, can give a rough estimate of the pH value of an acid or base without conducting experiments. However, these indicators may not be as accurate as using the Henderson-Hasselbalch equation or online pH calculators. Indicators can also be affected by external factors such as temperature and light, which can alter their color change and give inaccurate results.

3. What are some common acids and bases and their corresponding pH values?

Some common acids and their corresponding pH values include hydrochloric acid (pH 1), sulfuric acid (pH 2), vinegar (pH 3), and lemon juice (pH 2). Some common bases and their corresponding pH values include sodium hydroxide (pH 14), bleach (pH 12), baking soda (pH 9), and ammonia (pH 11). Keep in mind that the pH values of these substances may vary slightly depending on their concentration and purity.

4. How does the strength of an acid or base affect its pH value?

The strength of an acid or base refers to its ability to donate or accept hydrogen ions (H+) in a solution. The stronger the acid, the lower its pH value will be. This is because strong acids completely dissociate in water, releasing a high concentration of H+ ions, which lowers the pH. On the other hand, strong bases have a high pH value because they readily accept H+ ions from water, decreasing the concentration of H+ ions and increasing the pH.

5. Can the pH value of an acid or base change over time?

Yes, the pH value of an acid or base can change over time due to various factors such as dilution, reaction with other substances, or exposure to air. For example, if an acidic solution is diluted, the concentration of H+ ions decreases, resulting in a higher pH value. Additionally, acids can react with metals or bases, changing their pH value. It is important to regularly monitor the pH of solutions in order to accurately track any changes over time.

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