瓶内余下氧气密度是: 4 kg/m³ 过程：设原质量为m,体积为v 密度p0 = m / v = 6用去1/3剩余氧气的质量为：m * 2/3体积不变为v 剩余氧气的密度为:p1 = m*（2/3) / v = (2/3) * m / v = (2/3) * p0 =(2/3) * 6kg/...