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denis23 [38]
3 years ago
7

A chemist must prepare 200.0 mL of hydrochloric acid solution with a pH of 0.60 at 25 °C. He will do this in three steps: • Fill

a 200.0 mL volumetric flask about halfway with distilled water. • Measure out a small volume of concentrated (6.0M) stock hydrochloric acid solution and add it to the flask. • Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrochloric acid that the chemist must measure out in the second step. Round your answer to 2 significant digits. mL X 5 ?
Chemistry
1 answer:
Likurg_2 [28]3 years ago
5 0

Answer:

In the second step, the chemist must measure 8.3 ml of concentrated acid

Explanation:

The concentration of the final solution can be obtained using the pH value:

pH = -log[H] = 0.60

[H] = 10^(-0.60) = 0.25 M

Then, the final concentration of HCl will be 0.25 M because HCl is a monoprotic acid, which means that HCl only has one hydrolyzable proton. Therefore: [HCl] = [H].

The number of moles of HCl in the final solution will be equal to the number of moles present in the volume taken from the stock solution:

n° of moles in the volume taken from stock solution = n° moles in the final solution.

The number of moles can be calculated as follows:

number of moles = concentration * volume

Then:

Ci * Vi = Cf * Vf

where

Ci = concentration of the stock solution

Vi = volume taken from the stock solution

Cf = concentration of the final solution

Vf = volume of the final solution

Replacing with the data, we can obtain Vi:

6.0 M * Vi = 0.25 M * 200.0 ml

<u>Vi = 8.3 ml</u>

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You are asked to construct a segment bisector by paper folding. which is the best description your process? a use a ruler to mea
Orlov [11]

The best description of the process to draw the segment is B. b place a compass at one endpoint of the segment and trace an arc. do the same from the other endpoint. draw a line through the intersections of the arcs.

<h3>What is a segment bisector?</h3>

It should be noted that a segment bisector simply means a line to segment which cuts another line segment at the center but dividing the lines into two equal halves.

In this case, based on the information given, the best description of the process to draw the segment is to place a compass at one endpoint of the segment and trace an arc, do the same from the other endpoint. draw a line through the intersections of the arcs.

In conclusion, the correct option is B.

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brainly.com/question/2437195

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6 0
2 years ago
A sample of iron metal is placed in a graduated cylinder. it is noted that 10.4 ml of water is displaced by the iron. the iron i
Pavel [41]
<h3>Answer:</h3>

                 162.43 g of FeCl₂

<h3>Explanation:</h3>

Step 1: Calculate mass of Fe;

As,

                                   Density  =  Mass ÷ Volume

Or,

                                   Mass  =  Density × Volume

Where Volume is the volume of water displaced  =  10.4 mL

Putting values,

                                   Mass  =  7.86 g.mL⁻¹ × 10.4 mL

                                   Mass  =  81.744 g of Fe

Step 2: Calculate amount of FeCl₂;

The balance chemical equation is as follow,

                                Fe  +  2 HCl   →    FeCl₂  +  H₂ ↑

According to this equation,

       55.85 g (1 mol) Fe produced  =  110.98 g (1 mol) of FeCl₂

So,

               81.744 g Fe will produce  =  X g of FeCl₂

Solving for X,

                    X  =  (81.744 g × 110.98 g) ÷ 55.85 g

                     X =  162.43 g of FeCl₂

7 0
3 years ago
Calculate the concentrations of all species present in a 0.26 M solution of ethylammonium chloride (C2H5NH3Cl).
Alina [70]

Answer:

0.00000223

Explanation:

pKa for C2H5NH3+ = 10.7

pKw = 14.0

pKa + pKb = pKw

10.7 + pKb = 14.0

pKb = 14.0 - 10.7

pKb = 3.30

C2H5NH3Cl is a salt of ethylamine and HCl so it will dissolve in water to produce  C2H5NH3^+ + Cl^-

The base hydrolysis reaction:  C2H5NH3^+(aq) + H2O(l) <=> C2H5NH2(aq) + H3O^+(aq)

This reaction is described by Kb.

Kb = [C2H5NH2][H3O^+]/[C2H5NH3^+]

Let [C2H5NH2] = [H3O^+] = x,

so [C2H5NH3^+] = 0.26 - x

Kb = x^2/(0.26 - x) = 2.00 x 10^-11  

Let's solve for x. In this equation,  It is possible to solve without the use quadratic equation. So we can assume that 0.26 - x  is approximately equal to 0.26.  We won't know until we do the calculation.

We get:  x^2 + 2.00 x 10^-11x - 4.99 x 10^-12 = 0

With the use of a quadratic calculator.

x = 2.23 x 10^-6 M = [C2H5NH2] = [H3O^+]

0.26 - x  is just 0.26 M in this problem because 2.23 x 10^-6 M is insignificant.

[C2H5NH3^+] = 0.26 M = [Cl^-]

NOTE:

pH = -log [H3O^+] = -log(2.23 x 10^-6) = 5.65

Ka is the acid dissociation constant

Kb is the base dissociation constant

5 0
3 years ago
HELPP please I’ll mark you as brainlister it’s 100 points
Andrei [34K]

Answer:

4

Explanation:

hope this helps, can i have brainliest

4 0
3 years ago
How many moles of Mg3(PO4)2 are in 350.00 grams of Mg3(PO4)2?
dusya [7]

Answer:

1.3 moles/ 1.33150727 moles

Explanation:

350g x 1 mol/262.86g = 1.3 moles

6 0
3 years ago
Read 2 more answers
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