VCAA Chem Questions.

[geoff_821]

Okay I have a number of questions to ask with some of the VCAA exams.

First of all: significant figures.
Do we only take into account of the values we have used.
E.g. if we have to calculate the moles of something and mass = 5.1234g, Molar mass = 123g/mol and Concentration = 0.14M
Coz we are calculating moles, where only the mass and molar mass is relevant, would the number of significant figures be 3? (123g/mol) or would it be 2 sig figs, coz they gave us the concentration (0.14M) in the question?

VCAA 2008 Multiple choice Q8.
I understand we have to take into account the mole ratios, but why does [H2] increase twice as much as [I2] when they have the same mole ratio?

VCAA 2008 Multple choice Q12.
I have no idea. I'm pretty clueless when it comes to strong ionisation and weak ionisation, can someone clarify this all for me?

VCAA 2008 Extended Response Q3e.
Once again, I don't understand ionisation with strong/weak acids/bases. Can someone explain


That's all, thanks heaps!

[burbs]

First of all: significant figures.
Do we only take into account of the values we have used.
E.g. if we have to calculate the moles of something and mass = 5.1234g, Molar mass = 123g/mol and Concentration = 0.14M
Coz we are calculating moles, where only the mass and molar mass is relevant, would the number of significant figures be 3? (123g/mol) or would it be 2 sig figs, coz they gave us the concentration (0.14M) in the question?

Sigfigs are for the values used in that calculation.

[geoff_821]

First of all: significant figures.
Do we only take into account of the values we have used.
E.g. if we have to calculate the moles of something and mass = 5.1234g, Molar mass = 123g/mol and Concentration = 0.14M
Coz we are calculating moles, where only the mass and molar mass is relevant, would the number of significant figures be 3? (123g/mol) or would it be 2 sig figs, coz they gave us the concentration (0.14M) in the question?

Sigfigs are for the values used in that calculation.

Cheers, let's say you had to bring in a value from your data book, and it has 2 sig figs, would your answer be in 2 also?

[zool3]

of all the given information (question or data), use the one with the lowest sigfig