Answer:
When you move the burette slider to the top of a flask and add about 25 mL of NaOH to the flask, you will cause a concentration of OH- molecules. This will make the solution become a basic solution and make the litmus paper blue.
Explanation:
After reading your question, we can see that you are carrying out a test to discover the nature of the pH of a solution. This type of test uses litmus paper, which is an indicator of the presence of acids and bases, being able to determine the pH of a solution. This paper is soaked in organic ink and when placed in an acidic solution, it is red in color. However, when placed in a basic solution it has a blue color.
An acidic solution is one that has a high concentration of H+ atoms and has the ability to donate electrons. The basic solution, on the other hand, has a high concentration of OH- and has the capacity to receive electrons.
When you move the burette slider to the top of a flask and add about 25 mL of NaOH to the flask, you will cause a concentration of OH- molecules. This will make the solution become a basic solution and make the litmus paper blue, that is, the solution has the basic pH.
Question #1
Potasium hydroxide (known)
volume used is 25 ml
Molarity (concentration) = 0.150 M
Moles of KOH used
0.150 × 25/1000 = 0.00375 moles
Sulfuric acid (H2SO4)
volume used = 15.0 ml
unknown concentration
The equation for the reaction is
2KOH (aq)+ H2SO4(aq) = K2SO4(aq) + 2H2O(l)
Thus, the Mole ratio of KOH to H2SO4 is 2:1
Therefore, moles of H2SO4 used will be;
0.00375 × 1/2 = 0.001875 moles
Acid (sulfuric acid) concentration
0.001875 moles × 1000/15
= 0.125 M
Question #2
Hydrogen bromide (acid)
Volume used = 30 ml
Concentration is 0.250 M
Moles of HBr used;
0.25 × 30/1000
= 0.0075 moles
Sodium Hydroxide (base)
Volume used 20 ml
Concentration (unknown)
The equation for the reaction is
NaOH + HBr = NaBr + H2O
The mole ratio of NaOH : HBr is 1 : 1
Therefore, moles of NaOH used;
= 0.0075 moles
NaOH concentration will be
= 0.0075 moles × 1000/20
= 0.375 M
0.0788 will be the number of moles of silver in coin.
<h3><u>How to find the number of moles?</u></h3>
A mole is the mass of a material made up of the same number of fundamental components. Atoms in a 12 gram example are identical to 12C. Depending on the material, the fundamental units may be molecules, atoms, or formula units.
A mole fraction shows how many chemical elements are present. The value of 6.023 x 10²³ is equivalent to one mole of any material (Avagadro's number). It can be used to quantify the chemical reaction's byproducts. The symbol for the unit is mol.
The number of moles formula is denoted by the following expression:
Number of moles = Mass of substance/mass of one mole
To view more about number of moles, refer to:
brainly.com/question/14080043
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Answer:
The answer is
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Explanation:
To find the number of atoms given the number of moles we use the formula
N = n × L
where
N is the number of entities
n is the number of moles
L is the Avogadro's constant which is
6.02 × 10²³ entities
From the question
Substitute the values into the above formula and solve
That's
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We have the final answer as
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Hope this helps you
