Random Question Thread.

[d0minicz]

ah got that aswell
answers say potassium chloride

"Potassium chloride. If the solution was potassium bromide, bromine would form at the positive anode and bromine is a red-brown liquid."

[ed_saifa]

oh wait i misunderstood the question. It's not mixed =.="

[chem-nerd]

the question said that the solution was EITHER potassium chloride or potassium bromide, not that both were present. thus, only your knowledge of what the products from either reaction were would help you determine which solution it was.

[d0minicz]

ohh okay

how would i deduce potassium chloride from that ?

[chem-nerd]

from the ECS Cl₂ is a gas and Br₂ is a liquid. From your general chemistry knowledge you should (hopefully) have encountered Cl₂ being a colourless gas and Br₂ being a red-brown liquid.

[d0minicz]

hey

you know when they give us questions about colour change on an equilibrium; eg: left side = blue , right side = red
say if you add a reactant, the reaction would proceeed to the right, thus increasing the intensity of the red
but does the initial increase in conc of the reactant (blue) affect the end colour?

also: equilibrium questions without the colour part
Say if pressure was increased and the reaction proceeded to the right, the initial pressure would increase the conc. of all right? So even though the reaction proceeds to the right, the conc. of the reactants is still higher due to the initial increase yeah...?

im getting confused between these two types of q's

thanks =]

[Mao]

1. yes, the colour change will be more red, less blue. However, they won't give you these style of questions in a way that is too ambiguous. You can generally assume the favoured colour (by the equilibrium) to be dominant.

2. absolutely correct.

[james207]

hey just a quick question from the STAV 08 paper:

Question 3:

An excess of zinc powder was added to 50mL of 0.100 M AgNO3 (aq) in a polystyrene cup. Initially the temperature of the solution was 21.10 C and during the reaction it rose to 25.40 C. Assuming that the density of the solution is 1.00 g/mL and ignoring heat capacity of the metals, calculate the enthalpy change for the reaction.

The main problem I am having is determining the m value to sub into E=mcT

Thanks 

[nerd]

The mass of the solution would simply be 50g since density if 1.00g/mL.

[james207]

The mass of the solution would simply be 50g since density if 1.00g/mL.

how did i overlook that lol, thanks