Under what conditions does a gas behave ideally? Why?

When the applied pressure is $16 \ atm$,the temperature is $27 \ ^oC$,and the volume is $9 \ L$,what will be the weight of $CH_4$ gas in $gm$? (Given $R = 0.08 \ L \ atm \ K^{-1} \ mol^{-1}$)

At what $^o C$ temperature,the sample of neon gas would be heated to double its pressure,if the initial volume of gas is reduced to $15\%$ at ${75\,^o}C$?

If $2.5$ moles of an ideal gas at a certain temperature are allowed to expand isothermally and reversibly from an initial volume of $2$ $dm^3$ to $20$ $dm^3$, the work done by the gas is $-16.5$ $kJ$. The temperature (in $K$) of the gas is (Round off to the nearest value). $(R = 8.314 \ J \ K^{-1} \ mol^{-1})$

Choose the correct option for the graphical representation of Boyle's law,which shows a graph of pressure vs. volume of a gas at different temperatures:

At a temperature of $27\,^oC$ and a pressure of $1\,atm$,the density of a gas is $d$. At constant pressure,at what temperature will its density become $0.75\,d$?