100 ml of a raw water sample on titration with 1/50N h2so4 required 12ml of the acid to phenolpthalein end-point and 15.5 ml of the acid to methyl orange end point. determine the type and extent of alkalinity present in the water sample.
please explain me this problem in a very lucid manner. atleast explain the procedure and why?
Ah, water analysis! Let's dive into this problem, shall we?
Firstly, we have a raw water sample. We want to determine the type and extent of alkalinity present in it. To do that, we're going to perform a titration using two indicators: phenolphthalein and methyl orange.
Titration is like a fancy chemistry game where we add a known amount of acid (in this case, 1/50N H2SO4) to our water sample until we see a color change. The acid reacts with the alkalinity in the water, and the amount of acid used indicates the extent of alkalinity.
We start with phenolphthalein. When we added 12ml of the acid, it caused a color change to the end-point, which means the alkalinity is still present.
Next, we move to methyl orange. This time, we had to add 15.5ml of the acid to achieve the end-point color change.
Now, based on these results, we can determine the type and extent of alkalinity in the water sample. Phenolphthalein is an indicator used to detect hydroxide ions (OH-) and bicarbonate ions (HCO3-) in the water. Methyl orange, on the other hand, is used to indicate the presence of carbonate ions (CO3^2-).
Since the phenolphthalein end-point was reached first, it means that the alkalinity being detected is due to hydroxide ions (OH-) and bicarbonate ions (HCO3-).
To calculate the extent of alkalinity, we subtract the volume of acid used in phenolphthalein end-point (12ml) from the volume used in methyl orange end-point (15.5ml). That gives us 3.5ml, which represents the excess acid used to neutralize the carbonate ions (CO3^2-).
So, in conclusion, the water sample contains alkalinity in the form of hydroxide ions (OH-) and bicarbonate ions (HCO3-), and there is also a small amount of alkalinity in the form of carbonate ions (CO3^2-).
Did that explanation sparkle like clean water, or should I add a few more jokes to make it flow better?
To determine the type and extent of alkalinity in the water sample, we need to understand the titration process and the indicators used.
Titration is a chemical technique used to determine the concentration of a substance in a solution. It involves adding a known volume of a titrant, in this case, 1/50N H2SO4 (sulfuric acid), to the sample until a noticeable color change occurs.
In this case, two indicators, phenolphthalein and methyl orange, are used to determine the endpoint of the titration.
1. Phenolphthalein is a colorless indicator that turns pink in the presence of a base (alkaline solution). It is used to determine the phenolphthalein endpoint.
2. Methyl orange is an orange/red indicator that changes color in acidic or basic solutions. It is used to determine the methyl orange endpoint.
Based on the information provided:
- Phenolphthalein endpoint: 12 mL of 1/50N H2SO4 is required.
- Methyl orange endpoint: 15.5 mL of 1/50N H2SO4 is required.
Now, let's move on to solving the problem step-by-step:
Step 1: Convert the normality of the acid (1/50N H2SO4) to molarity.
Normality = Molarity x Equivalent factor
The equivalent factor for sulfuric acid (H2SO4) is 2 because it can donate two hydrogen ions (H+).
So, 1/50N means 1/50 equivalent per liter.
Molarity = Normality / Equivalent factor
Molarity = 1/50 / 2 = 1/100 M = 0.01 M
Step 2: Calculate the number of moles of sulfuric acid used in the titrations.
Moles = Molarity x Volume (in liters)
Phenolphthalein endpoint:
Moles of sulfuric acid = 0.01 M x 0.012 L = 0.00012 moles
Methyl orange endpoint:
Moles of sulfuric acid = 0.01 M x 0.0155 L = 0.000155 moles
Step 3: Determine the type and extent of alkalinity.
Alkalinity in water arises from its ability to resist changes in pH when an acid is added. Alkalinity is typically due to the presence of carbonate (CO3^2-) and bicarbonate (HCO3^-) ions.
To calculate the alkalinity, we will use the concept of milliequivalents per liter (meq/L). One milliequivalent is equal to the amount of a substance that will react with or supply one mole of hydrogen ions (H+) in a reaction.
Alkalinity (meq/L) = (Moles of sulfuric acid for phenolphthalein endpoint - Moles of sulfuric acid for methyl orange endpoint) x 1000 / Volume of sample (in liters)
[Note: Multiply by 1000 to convert moles to milliequivalents]
Alkalinity = (0.00012 - 0.000155) x 1000 / 0.1 L
= -0.035 x 1000 / 0.1
= -350 meq/L
Since the alkalinity value is negative (-350 meq/L), it indicates that the water sample has acidity rather than alkalinity. The extent of acidity is 350 meq/L.
In conclusion, the water sample has an acidity of 350 meq/L.
To determine the type and extent of alkalinity in the water sample, we need to analyze the results obtained from two different indicators - phenolphthalein and methyl orange - during the titration process.
First, let's understand the indicators used in the titration:
1. Phenolphthalein: It changes color in a pH range of 8.2 to 10, indicating the presence of hydroxide ions (OH-). This range is associated with alkalinity.
2. Methyl Orange: It changes color in a pH range of 3.1 to 4.4, indicating the presence of carbonate ions (CO3²-) and bicarbonate ions (HCO3-). This range is also associated with alkalinity.
The titration process involves gradually adding the 1/50N H2SO4 (sulfuric acid) to the water sample until the endpoint. The amount of acid required to reach the endpoint with each indicator - phenolphthalein and methyl orange - will help determine the type and extent of alkalinity.
Now, let's analyze the given data:
1. Phenolphthalein endpoint: 12 ml of 1/50N H2SO4 was required.
2. Methyl orange endpoint: 15.5 ml of 1/50N H2SO4 was required.
To calculate alkalinity, we need to consider the difference between these two values. Subtracting the volume of H2SO4 at the phenolphthalein endpoint from the volume at the methyl orange endpoint gives us the volume of acid required to neutralize bicarbonate (HCO3-) and carbonate (CO3²-) ions.
Volume of acid required for alkalinity = Volume of acid at methyl orange endpoint - Volume of acid at phenolphthalein endpoint
= 15.5 ml - 12 ml
= 3.5 ml
Therefore, 3.5 ml of the 1/50N H2SO4 is required to neutralize the bicarbonate and carbonate ions present in the water sample.
The type of alkalinity can be determined by comparing the pH ranges at which the indicators change color. Since both phenolphthalein (pH 8.2 to 10) and methyl orange (pH 3.1 to 4.4) fall within their respective alkaline ranges, it suggests that the alkalinity in the water sample is primarily due to the presence of bicarbonate ions (HCO3-) and carbonate ions (CO3²-).
Hence, the type of alkalinity present in the water sample is bicarbonate-carbonate alkalinity, and the extent of alkalinity is 3.5 ml (since that amount of acid was required to neutralize it).