QUESTION: Consider the reaction: N2 + 3 H2  2 NH3 Suppose 0.500 mol of N2 is used up in this reaction. How much NH3 is produced? A. 4.26 g, B. 8.50 g, C. 17.0 g Consider the reaction: N2 + 3 H2  2 NH3 Suppose a reaction mixture initially contained 0.800 mol N2, and now contains only 0.500 mol N2 as a result of the reaction, how much H3 was consumed? A. 0.100 mol, B. 0.900 mol, C. 0.300 mol PAUSE CLICK CONTINUED ON NEXT SLIDE

QUESTION: Consider the reaction: N2 + 3 H2  2 NH3 Suppose 0.500 mol of N2 is used up in this reaction. How much NH3 is produced? A. 4.26 g, B. 8.50 g, C. 17.0 g 17.03 g NH3 2 mol NH3 0.500 mol N2 x x 1 mol N2 1 mol NH3 CLICK We’re given that the amount of nitrogen consumed in the reaction is 0.500 moles. To calculate the amount of ammonia produced, all we have to do is multiply the moles of nitrogen consumed by a conversion factor. CLICK CLICK We use the coefficients in the balanced equation to construct our conversion factor. Since we’re interested in ammonia, we put the coefficient of ammonia in the numerator CLICK The coefficient of ammonia in the balanced equation is 2. HIGHLIGHT 2 in balanced equation and 2 in numerator ... and put the coefficient of nitrogen in the denominator CLICK The coefficient of N2 in the balanced equation is 1. HIGHLIGHT 1 in balanced equation and 1 in denominator The ratio of coefficients serves as a conversion factor. SHOW CANCELLATION OF UNITS An the answer we get here is 1.00 moles of ammonia. CALLOUT “= 1.00 mol NH3” But the choices given to us are in grams. So we need to convert our answer to grams By now, you should know how to do this. We multiply moles of ammonia by CLICK CLICK the molar mass of ammonia Carrying out the calculation gives an answer of 17.0 grams. Note that we keep three significant digits in our answer since the least precise term in our calculation, 0.500, has only three significant digits. The numbers 2 and 1 in the conversion factors are exact, while the molar mass 17.03 has four significant digits. Therefore, the correct answer is C. CLICK PAUSE END RECORDING = 17.0 g NH3

Video ID: 4-8-3 © 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