WEBVTT

00:00:05.400 --> 00:00:11.213
In this video, we will be investigating a
strong acid, strong base titration with

00:00:11.213 --> 00:00:17.870
our Go Direct pH Sensor, and our Go Direct
Drop Counter. A titration is a process

00:00:17.870 --> 00:00:22.450
used to determined the volume of a
solution needed to react with a given

00:00:22.450 --> 00:00:27.290
amount of another substance. In this
experiment, you will titrate hydrochloric

00:00:27.290 --> 00:00:33.030
acid with a basic sodium hydroxide
solution. To get started, I want to make

00:00:33.030 --> 00:00:36.180
sure I have assembled
my titration apparatus.

00:00:36.180 --> 00:00:42.850
I have my stir station, with the utility
clamp holding my reagent reservoir for the

00:00:42.850 --> 00:00:48.380
drop counter. Sodium hydroxide is in the
reagent reservoir. The drop counter is

00:00:48.380 --> 00:00:54.000
attached, the pH probe is in the electrode
opening, and the drops from the reagent

00:00:54.000 --> 00:01:00.000
reservoir go through this opening. In the
beaker, I have a magnetic stirring bar,

00:01:00.000 --> 00:01:05.820
10 milliliters of hydrochloric acid,
and 30 milliliters of distilled water,

00:01:05.820 --> 00:01:09.470
with a few drops of
phenolphthalein indicator.

00:01:09.470 --> 00:01:16.020
The Go Direct pH Sensor and Drop Counter
can be connected via USB or via Bluetooth

00:01:16.020 --> 00:01:21.850
to your platform. The platform can
be a ChromeBook, Mac computer,

00:01:21.850 --> 00:01:27.910
Windows computer, iOS, or Android
device. To get started, make sure you have

00:01:27.910 --> 00:01:32.920
downloaded the Graphical Analysis 4 app
from our website, or from the appropriate

00:01:32.920 --> 00:01:34.360
app store.

00:01:34.360 --> 00:01:39.663
Since I will be taking data via Bluetooth,
I will now turn on my pH probe and drop

00:01:39.663 --> 00:01:53.700
counter. I'll then launch the GA4 app,
and select Sensor Data Collection.

00:01:59.100 --> 00:02:11.270
I'll then connect to my pH probe,
and to my drop counter. Select 'Done'.

00:02:11.270 --> 00:02:16.420
Since my titration is all ready to go, and
the Graphical Analysis 4 software has

00:02:16.420 --> 00:02:22.130
auto-identified my drop counting mode of
data collection, I can go ahead and press

00:02:22.130 --> 00:02:26.980
the 'Collect' button, and it
will wait until the first drop

00:02:26.980 --> 00:02:29.006
passes through the slot.

00:02:29.006 --> 00:02:33.556
At this point, I can open the
stopcock on my reagent reservoir,

00:02:33.556 --> 00:02:38.090
and the drops will go through the slot,
and I see the indication of that on the

00:02:38.090 --> 00:02:44.070
drop counter and on the software. The
drops should be coming out at about one

00:02:44.070 --> 00:02:51.100
per second. The slower the
drops, the better the titration data.

00:03:30.900 --> 00:03:39.487
Once my titration is complete, I can close
the stopcock and stop the data collection.

00:03:39.487 --> 00:03:44.070
Now, I have a little bit of work to do
to determine the equivalence point.

00:03:44.070 --> 00:03:48.950
I have a few different options for
determining this. First, I can tap along

00:03:48.950 --> 00:03:57.300
the graph, and find the volume where
the pH changes most dramatically.

00:03:57.300 --> 00:04:02.696
Alternatively, I can take the derivative,
which will give me a peak where the change

00:04:02.696 --> 00:04:04.980
in pH is steepest.

00:04:04.980 --> 00:04:11.694
To calculate and graph this, I
need to add a calculated column.

00:04:11.694 --> 00:04:15.700
First, I will remove the examine line.

00:04:15.700 --> 00:04:22.330
And then from the square icon,
change the view to Graph and Table.

00:04:22.330 --> 00:04:25.779
Then, I click on the
dots in the pH column,

00:04:25.779 --> 00:04:31.879
and select 'Add Calculated Column'.

00:04:31.879 --> 00:04:38.172
I will rename this "First Derivative."

00:04:43.150 --> 00:04:46.979
Tap on 'Insert Expression',
and select 'First Derivative',

00:04:46.979 --> 00:04:48.698
making sure column Y is

00:04:48.698 --> 00:04:58.540
volume, and column X is pH. Tap 'Apply'.
To autoscale, double-click anywhere on the

00:04:58.540 --> 00:05:07.800
graph. Now, to get the volume where
this peak of my first derivative happens,

00:05:07.800 --> 00:05:12.320
I can use the statistics feature
in Graphical Analysis. To do that,

00:05:12.320 --> 00:05:19.550
I select the Graph Tools icon, 'View
Statistics', and scroll down to the First

00:05:19.550 --> 00:05:27.210
Derivative data, where the max
is occurring at 8.393 milliliters.

00:05:27.210 --> 00:05:31.510
Knowing the precise equivalence point, I
can determine the exact concentration of

00:05:31.510 --> 00:05:37.060
my hydrochloric acid. For more information
about the Vernier Go Direct pH probe,

00:05:37.060 --> 00:05:42.930
Drop Counter, and our entire line of Go
Direct sensors, visit our website or email

00:05:42.930 --> 00:05:44.400
info@vernier.com