The flask contains 10.0 mL of HCl and a few drops of phenolphthalein indicator. The buret contains 0.150 M NaOH. It requires 21.4 mL of the NaOH solution to reach the end point of the titration. A buret filled with a titrant is held above a graduated cylinder containing an analyte solution. What is the initial concentration of HCl

0.321 M

Explanation:

The neutralization reaction of HCl with NaOH is the following:

HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

So, 1 equivalent of HCl reacts with 1 equivalent of NaOH. In this case:

1 equivalent HCl = 1 mol HCl

1 equivalent NaOH = 1 mol NaOH

At the equivalence point, the amount of HCl reacts completely with the added amount of titrant (NaOH). As 1 mol of reactant is calculated from the product of the molarity of the solution and the volume, in the equivalent point:

moles HCl = moles NaOH

M(HCl) x V(HCl) = M(NaOH) x V(NaOH)

We have:

M(NaOH) = 0.150 M

V(NaOH) = 21.4 mL = 0.0214 L

V(HCl) = 10.0 mL = 0.01 L

Thus, we calculate the initial concentration HCl as follows:

M(HCl) = (M(NaOH) x V(NaOH))/ (V(HCl))

            = (0.150 M x 0.0214 L)/(0.01 L) = 0.321 M

false

because it does not have the potential to be entirely used up

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.