if the edge length of a NaH unit cell is 488 pm, what is the length of Na-H bond if it crystallises in the fcc structure ?
A. 122 pm
B. 244 pm
C. 488 pm
D. 976 pm
A. 122 pm
B. 244 pm
C. 488 pm
D. 976 pm
Correct Answer – B
NaH has fcc structure similar to that of NaCl. Thus, edge length of NaH=`2(r_(Na^+)+(r_H^(-))` i.e., `2(r_(Na^+)+r_(H^-))`=488 pm
`therefore r_(Na^+)+r_(H^-)`=244 pm, which is Na-H bond length
Correct Answer – d
NaH has fcc structure similar to that of NaCl. ltbr. Thus, edge length of NaH =` 2( r_(Na^(+)) + r_(H^(-)))`
i.e, ` 2( r_(Na^(+) + r_(H^(-)) = 488 “pm” `
i.e, ` 2( r_(Na^(+)) + r_(H^(-))) = 488 “pm”`
` r_(Na^(+)) + r_(H^(-)) = 244 “pm”` , which is Na -H bond length.