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Page No 177: - Chapter 7 - P - Block Elements - Intext Solutions - Ncert Solutions class 12 - Chemistry

Updated On 11-02-2025 By Lithanya


Question 7.7:

Bond angle in https://img-nm.mnimgs.com/img/study_content/curr/1/12/17/266/6577/NS_14-11-08_Sonali_12_Chemistry_7_34_html_m51afeb08.gif is higher than that in PH3. Why?

Answer:

In PH3, P is sp3 hybridized. Three orbitals are involved in bonding with three hydrogen atoms and the fourth one contains a lone pair. As lone pair-bond pair repulsion is stronger than bond pair-bond pair repulsion, the tetrahedral shape associated with sp3 bonding is changed to pyramidal. PH3 combines with a proton to form https://img-nm.mnimgs.com/img/study_content/curr/1/12/17/266/6577/NS_14-11-08_Sonali_12_Chemistry_7_34_html_m51afeb08.gif  in which the lone pair is absent. Due to the absence of lone pair inhttps://img-nm.mnimgs.com/img/study_content/curr/1/12/17/266/6577/NS_14-11-08_Sonali_12_Chemistry_7_34_html_m51afeb08.gif , there is no lone pair-bond pair repulsion. Hence, the bond angle in https://img-nm.mnimgs.com/img/study_content/curr/1/12/17/266/6577/NS_14-11-08_Sonali_12_Chemistry_7_34_html_m51afeb08.gif is higher than the bond angle in PH3.

https://img-nm.mnimgs.com/img/study_content/curr/1/12/17/266/6577/NS_14-11-08_Sonali_12_Chemistry_7_34_html_m5d792c00.jpg

Question 7.8:

What happens when white phosphorus is heated with concentrated NaOH solution in an inert atmosphere of CO2?

Answer:

White phosphorous dissolves in boiling NaOH solution (in a CO2 atmosphere) to give phosphine, PH3.

https://img-nm.mnimgs.com/img/study_content/curr/1/12/17/266/6579/NS_14-11-08_Sonali_12_Chemistry_7_34_html_7f0493fc.gif