VCE Chemistry Question Thread

[LPadlan]

A 200 mL beaker of water at a temperature of 21.0C is heated with 10.0kJ of energy. Calculate the temperature reached by the beaker of water

[sweetiepi]

A 200 mL beaker of water at a temperature of 21.0C is heated with 10.0kJ of energy. Calculate the temperature reached by the beaker of water

\(200 \text{mL} \approx 200\text{g}\)
\(10 \text{kJ} = 10 \times 10^3 \text{J}\)
\(\Delta \text {H}= c \times m \Delta T\)
\(\therefore \Delta \text{T} = \frac {\Delta \text{H}}{c \times m}\)
\(\therefore  \Delta \text{T}= \frac{10 \times 10^3}{4.18 \times 200}\)
\(\therefore \Delta \text{T} = 11.96 \text {(4sf- I have more in my calc)}\)
\(\Delta \text{T} =11.96 \text{ and T(i)} =21 \text{, T(f)} = 11.96 + 21.0 \text{ As T(final)= T(initial)}+ \Delta \text{H} \)
\(\therefore \text{T(final)}= 32.96 = 33.0 \text{ (to 3 sf)}\)

Sorry if I have a few mistakes, I'm a tad rusty!

[lasagne]

Hey all! I was just wondering if in a question you were given data about water being heated and then asked to work out the heat of combustion of the fuel in kj/mol, would you take into consideration the equation of the combustion of the fuel? Does it refer to the heat of combustion for the equation, or for 1 mole?
I've seen it done different ways and am very confused :/

[arushi]

hey.! Can someone explain me why does pH of water falls as temprature increases? i know that hydronium ion conc. increases so pH decreases but why don't we consider and increase in OH- ion as well which account for increase in pH?

[exit]

Any recommendations of Chem safety glasses? Preferable wit rubbery material and good feeling material on nose bridge etc.

I've realised I avoided pracs since year 7 because the glasses my school uses are all not that comfortable and scratched up so you can barely see through them.

[TheAspiringDoc]

Hi
Are lanthanides and actinides considered main group metals or transition metals? Do they share their chemical properties with main group metals or transition metals? Also, what defines something to be a metal - is it just its properties?
Sorry for these really straightforward questions, but I can't find an answer on the web or my textbook!

[peanut]

Can someone confirm these values for me? I know VCAA changed some of these for the 2017 study design, so I just want be sure these are right.

1 atm = 1.013 bar = 101.3 kPa = 760 mmHg
SLC is defined as 100 kPa at 25 degrees C.
STP is removed from the study design.

[cookiedream]

Can someone confirm these values for me? I know VCAA changed some of these for the 2017 study design, so I just want be sure these are right.

1 atm = 1.013 bar = 101.3 kPa = 760 mmHg
SLC is defined as 100 kPa at 25 degrees C.
STP is removed from the study design.

Yep! That's exactly what my teacher said.

[Syedali_]

Help
A 500mL volume of water in a beaker was heated using the energy released by the combustion of a 3 gram peice of wood. the temperature rise was 22.9C
 calculate the heat of combustion of wood in kJ/g and in MJ/tonne

[cookiedream]

Help
A 500mL volume of water in a beaker was heated using the energy released by the combustion of a 3 gram peice of wood. the temperature rise was 22.9C
 calculate the heat of combustion of wood in kJ/g and in MJ/tonne

Hello! I included my worked solutions with explanations.
Feel free to correct any mistakes I made.
(lol I just noticed that the question said that the water "was heated using the energy released" by the wood, so ignore my comment on assuming the energy content of the wood and water is the same)

[Syedali_]

Book answers says 16x10^4 kj/ grams

[cookiedream]

Book answers says 16x10^4 kj/ grams

Oh....
Hm, does the book have worked solutions??

[rachid.kam]

Book answers says 16x10^4 kj/ grams

Hi, which book is this and what section?

[Syedali_]

Hi, which book is this and what section?

Heinamen chemistry 2 5thedition 3/4 chapter review 2 question 19 a

[rachid.kam]

Oh....
Hm, does the book have worked solutions??

Hey cookiedream, really great attempt. However, you sort of stated that 47.9/3 is 15.9, then went on to state that it is 0.2x10^2. I think thats what stuffed up your calculations. My teacher clarified with us in class that the answers at the back of the book are wrong.