$a.PTHH : \\2C_2H_2+5O_2\overset{t^o}\to 4CO_2+2H_2O \\n_{C_2H_2}=\dfrac{2,24}{22,4}=0,1mol \\Theo\ pt : \\n_{O_2}=\dfrac{5}{2}.n_{C_2H_2}=\dfrac{5}{2}.0,1=0,25mol \\⇒V_{O_2}=0,25.22,4=5,6l \\b,Theo\ pt : \\n_{CO_2}=2.n_{C_2H_2}=2.0,1=0,2mol \\⇒m_{CO_2}=0,2.44=8,8g$