Question

The water in the gas-collecting apparatus is assumed to be 25C, but is actually 15C. How will this error affect the reported mass of aluminum in the sample?

Answer 1

since Al reacts with a gas to form hydrogen as per the reaction 2Al+ 6HCl ------>2AlCl3+ 3H2

when water is at less temperature, the vapor pressure of water is less. The vapor pressure of water at 15 deg.c is less than that of water at 25 deg.c. This leads to partial pressure of hydrogen being more at lower temperature. Hence moles of hydrogen increases and hence moles of Al also increases. the reported mass of Aluminium at 25 deg.c is less than that at 15 deg.c .