A certain sample of rainwater gives a yellow colour with...

A certain sample of rainwater gives a yellow colour with methyl red [pH range $4.2($ red $)-6.2($ yellow $)$ ]and a yellow colour with phenol red [pH range $6.4$ (yellow) $-8.0$ (red)]. What is the approximate $\mathrm{pH}$ of the water? Is the rainwater acidic, neutral, or basic? (a) $6.3$, acidic (b) $6.1$, acidic (c) $6.5$, acidic (d) $6.3$, basic

A certain sample of rainwater gives a yellow colour with methyl red [pH range $4.2($ red $)-6.2($ yellow $)$ ]and a yellow colour with phenol red [pH range $6.4$ (yellow) $-8.0$ (red)]. What is the approximate $\mathrm{pH}$ of the water? Is the rainwater acidic, neutral, or basic?
(a) $6.3$, acidic
(b) $6.1$, acidic
(c) $6.5$, acidic
(d) $6.3$, basic

Key Concepts

pH Scale

The pH scale is a logarithmic measure used to quantify the acidity or basicity of a solution, ranging from 0 to 14. Values below 7 indicate acidity, values above 7 indicate basicity, and a pH of 7 is neutral. This scale provides a standardized way to compare the chemical properties of different solutions.

Acid-Base Indicators

Acid-base indicators are chemical compounds that exhibit different colors at different pH levels, allowing for the estimation of a solution’s pH through visual observation. Each indicator has a specific pH range over which it changes color, making them practical tools in analytical chemistry to determine the acidic or basic nature of a substance.

Acid Rain

Acid rain refers to precipitation that has a lower pH than natural rainwater, often due to the presence of dissolved pollutants like sulfur dioxide and nitrogen oxides. Its slightly acidic nature is of environmental concern, as it can lead to harmful effects on ecosystems, infrastructure, and human health.

Transcript

00:01 In this video, we're going to be talking about ph.

00:04 And more specifically, we have an example here with finding out the ph of a sample of rainwater.

00:10 So here, i have just drawn a little vessel here that is labeled as rainwater.

00:16 And what had happened in this particular example is that we use two indicator dyes.

00:21 So indicator dyes pretty much allow you to essentially give you a ph range of the solution that you are testing.

00:28 And there are many indicator dyes.

00:31 Here we're just testing it with methyl red and bromidthmal blue.

00:35 And so whenever you place a solution within those indicator dyes, they may give off a certain color.

00:42 So it can be a range of color.

00:43 So for methyl red, it has a range of color going from red to yellow.

00:49 And then for bromidthamol blue, it goes from yellow to blue.

00:53 So it kind of has those particular types of range of colors.

00:56 So when a particular sample of rainwater was tested with methyl red, it gave off a yellow color, actually.

01:05 And so the yellow color here is a little bit hard to even just label here because there is no color yellow here for me to show you guys.

01:13 But as we mentioned with the methyl red, it has a ph range or a test a ph range from 4 .8 through 6.

01:21 And it goes from the color red to yellow.

01:24 So the yellow would most show up around here at this band length, right? and so when it was tested with bromethmal blue, brometh mal blue has tests a ph range from 6 to about 7 .6, more or less, give it or take...

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