cation–anion distances chemistry homework help

Question description

Unit V Problem Solving

In the ionic compounds LiF, NaCl, KBr, and RbI, the measured cation–anion distances are 2.01 Å (Li–F), 2.82 Å

(Na-Cl), 3.30 Å (K–Br), and 3.67 Å (Rb–I), respectively.

1. Predict the cation-anion distance of each ionic compound above using the values of ionic radii given in Figure 7.7

on page 257 in the textbook. To receive full credit, you must show how you predicted the distance for each

CHM 1030, General Chemistry I 3

molecule by providing a step-by-step solution for each molecule. The solution for each molecule is worth 8 points;

thus, a total of 32 total points is possible for this question.

2. Calculate the difference between the experimentally measured ion-ion distances provided at the beginning of this

assignment and the ones you have predicted in problem 1. You must show how you calculated the difference for

each molecule by providing a step-by-step solution for each molecule to get full credit (6 points for each molecule;

total possible points for this section is 24 points). Assuming that we have an accuracy of 0.04Å in the

measurement, please indicate for each molecule if your predicted ion-ion distances are accurate or not accurate

with respect to their experimental ion-ion distances (2 points for each molecule; total possible points for this

section is 12 points). A total of 32 total points is possible for this question.

3. What estimates of the cation-anion distance would you obtain for these four compounds using their bonding

atomic radii? (Note: these values are also in Figure 7.7 but are different from the ionic radii.) For each of the four

compounds, calculate the difference between the predicted ionic bond distance, which you calculated in problem

1, and predicted atomic bond distances you calculated in this problem. To receive full credit, you must show how

you calculated the difference for each molecule by providing a step-by step solution for each molecule (6 points

for each molecule; total possible points for this section is 24 points). Again, assuming that we have an accuracy of

0.04Å in the measurement, indicate for each molecule if your predictions are less or more accurate using the

atomic radii prediction method; explain your answer (2 points for each molecule; total points possible for this

section is 8 points). Using your knowledge of atomic and ionic radii trends in the periodic table, why might one

prediction method be more appropriate to use than the other in certain molecules (worth 4 points)? A total of 36

points is possible for this set of questions.