Mathematically, this implies that the ratio of the amount of element

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Presentation transcript:

Mathematically, this implies that the ratio of the amount of element QUESTION: A 17.0 g sample of a compound contains 14.0 g nitrogen and 3.0 g hydrogen. How much hydrogen does a 34.0 g sample of the compound contain? A. 3.0 g, B. 6.0 g, C. 14.0 g, C. 28.0 g The Law of Definite Composition says that the percentage of each element in any sample of the compound (as long as it’s pure) is constant. The ratio of amount of element to total amount is constant. Let x = amount of hydrogen in 34.0 g sample. SCRIPT: A 17.0 g sample of a compound contains 14.0 g nitrogen and 3.0 g hydrogen. How much hydrogen does a 34.0 g sample of the compound contain? A. 3.0 g, B. 6.0 g, C. 14.0 g, C. 28.0 g PAUSE CLICK. The Law of Definite Composition says that the percentage of each element in any sample of the compound (as long as it’s pure) is constant. CLICK Mathematically, this implies that the ratio of the amount of element to the total amount Is constant. If we let x be the amount of hydrogen in the 34.0 gram sample,… The ratio of x to 34.0 grams HIGHLIGHT would be equal to the ratio of 3.0 grams to 17.0 grams HIGHLIGHT To solve for x, we simply multiply both sides by 34.0 grams. CLICK and get x equals 6.0 grams of hydrogen. The correct answer is B. Let’s see if this makes sense…. 34 grams is twice as much as 17 grams. Therefore, we expect to have twice as much of everything. So, instead of 3 grams of hydrogen, we have 2 times 3, or 6 grams. PAUSE END RECORDING.

Video ID: 1-9-3 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08