[sam]

Consider the following reaction:
Zn(s)+ 2HCl(aq)--> ZnCl2(aq)+ H2(g)
Which of the following instruments could be used to monitor the rate of the reaction in an open system? 
 
1 balance
2 pressure gauge
3 pHmeter

does number 1 have anything to do with the question?
i chose 2 and 3

[Will]

Consider the following reaction:
Zn(s)+ 2HCl(aq)--> ZnCl2(aq)+ H2(g)
Which of the following instruments could be used to monitor the rate of the reaction in an open system? 
 
1 balance
2 pressure gauge
3 pHmeter

does number 1 have anything to do with the question?
i chose 2 and 3

In an open system I would assume the H₂ gas would be allowed to escape and make a negligible change to pressure, ruling out 2. However you can use a balance as the loss of H₂ would mean the mass of the solution falls allowing you to work out the rate of reaction. I think 1 and 3 are correct answers.

[sam]

In an open system I would assume the H₂ gas would be allowed to escape and make a negligible change to pressure, ruling out 2. However you can use a balance as the loss of H₂ would mean the mass of the solution falls allowing you to work out the rate of reaction. I think 1 and 3 are correct answers.

why? i thought the pressure would be decreased

[Will]

In an open system I would assume the H₂ gas would be allowed to escape and make a negligible change to pressure, ruling out 2. However you can use a balance as the loss of H₂ would mean the mass of the solution falls allowing you to work out the rate of reaction. I think 1 and 3 are correct answers.

why? i thought the pressure would be decreased

The pressure of what would decrease?

[sam]

ouh,
of the whole system?

[Will]

I think, because it is an open system, that hydrogen gas will simply escape the 'system' and the pressure won't change. The general definition of an open system is one whose border is permeable to both energy and mass. Under these circumstances I don't think H₂ will be allowed to build up in the system.