4.215 g of a metallic carbonate was heated in a hard glass tube and the CO2 evolved was found to measure 1336 mL at 27°C and 700 mm pressure. What is the equivalent weight of the metal?

Wt. of metal carbonate = 4.215 g;P1=700mm,V1=1336mLT1=27+273=300K; At NTPP2=760mm,V2=?,T2=273K.Using gas equation:                       P1V1T1=P2V2T2; V2=P1V1T1×T2P2;V2=700mm×1336mL×273K300K×760mm∴ V2( at NTP)=1119.8mLWe know that: wt. of metal carbonate VNTP in mL×11200mL =4.215×11200mL1119.8= Eq. wt. of metal carbonate  ∴     Eq. wt. of metal carbonate= 42.16∴    Eq. wt. of metal= Eq. wt. of metal carbonate - Eq. wt. of carbonate (CO3-2)                                    =42.16−[12+(3×16)]/2=42.16−30=12.16 Ans.