Chemistry Help: Neutralizing HCl & H3PO4 Solutions

  • Thread starter TJSR
  • Start date
  • Tags
    Chemistry
In summary, to neutralize 25ml of stomach acid with 0.10 M HCl, we need 0.0529g of Mg(OH)2. To neutralize 15ml of 0.20 M H3PO4 solution, we need 0.9 ml of 0.10 M NaOH. The equations and ratios were used to calculate the number of moles and then the mass or volume needed for neutralization.
  • #1
TJSR
2
0
HELP!

I need to know how to figure these problems out, while showing all
work so I can follow the steps...thanks for the help!

1. how many grams of Mg(OH)2 (2 is a subscript) will be needed to neutralize
25ml of stomach acid if stomach acid is 0.10 M HCl?

2. How many ml of a 0.10 NaOH solution are needed to neutralize 15ml of 0.20
M H3PO4 (subscripts) solution?
 
Chemistry news on Phys.org
  • #2
Please show your work first.
 
  • #3
All i can say if please use:

Ma x Mb / Va x Vb transpose for what you need.
 
  • #4
for number 1:

find out how many moles of HCl are in 25mL of a 0.10M solution by multiplying volume times molarity.

M HCl = 25mL x 1L/1000mL x 0.10mol / 1L

next calculate how many mL of xM [tex]Mg(OH)_2[/tex] solution contains the calculated number of moles of HCl. (I'm assuming you were given the molarity of [tex]Mg(OH)_2[/tex])

M HCl x 1L soln / M [tex]Mg(OH)_2[/tex] = x L of soln

convert L to mL, then you can multiply the answer by magnesium hydroxide's specific gravity (2.36) to get the amount in grams.


number 2 is the same approach but the answer is left in mL.
 
  • #5
Is it wrong here to assume that the production of Magnesium Chloride and water is a "neutralization" of the HCl? It sounds like a relatively elementary [HS Chem or Intro to Chem] level question, so a balanced eqn. and mole ratios could find how many grams of magnesium hydroxide are needed to completely react with all .025 L of HCl ... thus ridding the acid. Too simplified?
 
  • #6
Question one:

“How many grams of Mg(OH)2 (2 is a subscript) will be needed to neutralize
25ml of stomach acid if stomach acid is 0.10 M HCl?”

Display reaction equation (balanced) (Step 1)

Mg(OH)2+2HCl-->MgCl2+2H2O

1 to 2 ratio:

25ml of 0.10 M (INITIAL CONCENTRATION BEFORE DILUTION) of HCl (Step 2)

Concentration (M) = Number of moles / Volume

Therefore number of moles = concentration x volume (Step 3)

25ml = 0.025 dm^3

Number of moles = 0.10 x 0.025 = 0.0025 moles of HCl

Now back to Step 1, there is a ratio of 1:2, so we must divide answer by 2:

Moles in ratio = 0.0025 / 2 = 0.00125 (Step 4)

Now to get mass (amount in grams) (Step 5)

Mass (w) = Number of moles x Mr (Molecular mass)

Mr of Mg(OH)2 = 42.320g

Therefore w = 0.00125 x 42.320 = 0.0529g

So 0.0529g of Mg(OH)2 was needed to neutralise 0.0025 moles of Stomach acid (HCl).

Question 2:

“How many ml of a 0.10 NaOH solution are needed to neutralize 15ml of 0.20
M H3PO4 (subscripts) solution?”

H3PO4 + 3NaOH --> Na3PO4 + 3H2O (Step 1)

As we can deduce from the above equation there is a 1:3 ratio (Step 2)

Concentration (M) = Number of moles / Volume

Therefore number of moles = concentration x volume (Step 3)

15ml = 0.015 dm^3

0.20 x 0.015 = 0.003 moles of H3PO4

Since the ratio is 1:3 we must multiply the number of moles of H3PO4 by 3. (Step 4)
Mole(3NaOH) = 0.003 x 3 = 0.009.

Concentration (M) = Number of moles / Volume

Therefore Volume = Concentration x Number of moles: (Step 5)

Volume of (3NaOH) = 0.10 x 0.009 = 0.0009 dm^3

Volume in ml = dm^3 x 1000

Therefore volume of 3NaOH (in ml) = 0.0009 x 1000 = 0.9 ml of 3NaOH needed.
 

1. What is the purpose of neutralizing HCl and H3PO4 solutions?

The purpose of neutralizing these solutions is to balance the acidic pH and make the solution less corrosive and more suitable for various applications. This is achieved by adding a base, such as sodium hydroxide, which reacts with the acid to form a neutral salt and water.

2. How do you determine the amount of base needed to neutralize an acid solution?

The amount of base needed to neutralize an acid solution can be determined using the formula: moles of acid = moles of base. This means that the number of moles of the acid present in the solution should be equal to the number of moles of the base added to neutralize it.

3. Can you explain the concept of titration in neutralizing acid solutions?

Titration is a technique used to determine the concentration of an unknown solution by reacting it with a known solution of a base. In the case of neutralizing acid solutions, a burette is used to add the base to the acid solution until the equivalence point is reached. This is when the moles of the acid and base are equal, resulting in a neutral solution.

4. What are some common indicators used in neutralization reactions?

Some common indicators used in neutralization reactions are phenolphthalein, methyl orange, and bromothymol blue. These indicators change color at specific pH levels and can help determine when the solution has reached the equivalence point.

5. Can neutralization reactions produce any byproducts?

Yes, neutralization reactions can produce byproducts depending on the reactants used. For example, if a strong acid and a strong base are used, the byproduct will be water and a salt. However, if a weak acid and a strong base are used, the byproduct will also contain water and the conjugate base of the weak acid.

Similar threads

Replies
4
Views
1K
Replies
5
Views
4K
  • Chemistry
Replies
1
Views
1K
Replies
16
Views
2K
Replies
3
Views
7K
Replies
1
Views
852
  • Biology and Chemistry Homework Help
Replies
3
Views
1K
Replies
17
Views
2K
Replies
4
Views
12K
Back
Top