Sample I 5 has what mafic color index (MCI)? a. 0-15 % MCI b. 16-45 % MCI c. 46-85 % MCI d. >85

Sample I 5 has what mafic color index (MCI)? a. 0-15 % MCI...

Key Concepts

Mafic Color Index (MCI)

The Mafic Color Index is a quantitative measure used in igneous petrology to estimate the proportion of dark, mafic minerals present in a rock. Expressed as a percentage, it helps in assessing the mafic component, which in turn provides insights into the rock's composition, origin, and evolutionary history.

Mafic Minerals

Mafic minerals are igneous minerals that are rich in magnesium and iron and are typically dark in color. Their abundance within a rock influences physical properties and classification, making them critical in determining a rock's overall character and in evaluating the Mafic Color Index.

Transcript

00:01 Hello, and in this question here, we're going to be looking at a radioactive isotope iodine, which has 331 nucleons and 51 protons, and we're going to be looking at the activity of this sample of iodine.

00:16 So just before we start, the mass of one atom of this iodine is equal to, so the mass is equal to 131 .906.

00:33 2264u and the half -life of this sample of iodine or this isotope viadine is 0 .86 days or it is equal to 600 and 96 ,384 seconds okay and these figures here are just from the appendix in the back of the book so we're asked to determine we're given the activity of a sample of iodine, we're asked to determine the mass of iodine in that sample.

01:10 So the activity of a sample is defined as lambda times the number of nuclei in the sample.

01:19 Lambda is the decay constant and it has a value of the natural log of 2 divided by the half -life.

01:25 Okay? so the half -life is equal to, well the half -life is given us to us above, of 696 ,384 seconds.

01:36 So this means that a decay constant has a value of 9 .95 times 10 to the minus 7 with units of inverse seconds.

01:48 We're given from the question that the activity is equal to 64 .5 mili curie and the conversion between curie and bacarel is equal to, so one curie is equal to 3 .7 times 10 to the 7, backeret, sorry, 10 to the 10, baccerell, and we're converting into baccarell because baccarell is the si units of decay.

02:24 So, this means the activity in baccarell by converting the curie to bacorel.

02:33 This has an activity equal to 2 .386 times 10 to the 9 baccarrel.

02:43 So from here we have lambda, we have the activity.

02:51 So we're able to determine the number of nuclei at that given time.

02:55 So the number of nuclei is equal to the activity divided by lambda...

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