snowflake
Combusting 1 tonne of C3H8 releases 1.68 × 104 MJ

So the question is, how much energy does combusting 1 mol of C3H8 release?

So first you need to convert 1 tonne into mol:
1 tonne = 1 000 000 grams
n = m/M (n = number of moles, m = mass, M = molar mass)
M (C3H8) = 3 x 12 + 8 x 1 = 44 g/mol
n = 1 000 000 / 44 = 22727 mol

So if combusting 22727 mol of C3H8 releases 1.68 × 104 MJ, combusting 1 mol would release (1.68 x 104)/22727 MJ = 0.7392 MJ = 0.7392 x 1000 kJ = 739.2 kJ

Therefore, the ΔH value, in kJ mol–1, for the thermochemical equation is 739 kJ/mol.

    9 days later

    is there a difference between petrodiesel and petroleum gas or are they the same thing?

      mia46789

      Hi, yes there is a difference. Petrodiesel is 25% aromatic hydrocarbons and 75% alkanes which are in the C10H22-C15H32 range. Petroleum gas, on the other hand, is composed of much shorter alkanes, mainly propane (C3H8) and butane (C4H10).

      Another difference is that petrodiesel is a liquid, whereas petroleum gas, as the name suggests, is a gas, though it is usually stored under high pressures making it liquid petroleum gas (LPG).

      Both are usually obtained from crude oil.

          GreenAcorn I agree with the above, it's usually safe to assume that petrodiesel is dodecane (C12H26) and petroleum gas is propane. Likewise, you can assume petrol is octane

            13 days later

            im trying to calculate the heat of combustion for 3-methylbutan-1-ol in kj/g and kj/mol for this calorimetry experiment
            this is the information I have:
            mass of water (inside the metal can) (g) = 99.31 g
            initial mass of spirit burner (3-methylbutan-1-ol) (g) = 194.16 g
            final mass of spirit burner (g) = 193.8 g
            initial temperature of water (celsius) = 21.3 C
            final temperature of water (celsius) = 52.8 C
            I've been using the textbook to try and figure it out but I'm pretty sure the answer i keep getting is wrong

              bugsme_
              m(alcohol used) = 194.16 g - 193.8 g = 0.36 g

              energy released (assuming no heat loss to surroundings) = 99.31 g x 4.18 J/g/K x (52.8˚C - 21.3˚C) = 13076.1477 J

              Heat of combustion per g = 13.076... kJ / 0.36 g = 36.3 kJ/g

              Heat of combustion per mol = 13.076 kJ / (0.36 g / 88 g/mol) = 3196 kJ/mol

              However, since the final answer should be rounded to 3 sig figs (as temp was to 3 sig figs) and 3200 kJ/mol would be 4 sig figs according to VCAA, you would express this as 3.20 x 103 kJ/mol

                11 days later

                Hello!

                Does anyone have Chemistry AOS 1 practice sacs? I Have my sac on Thursday and my teacher has only given 2 TSSM sac's!!!

                2 months later

                hi,
                we just started the topic of fuel cells and i'm very confused. what's the connection between electrolytic, primary, secondary, voltaic, electrochemical cells?? we just did reduction and oxidation and that's fine but i can't seem to understand the whole 'batteries' thing.
                someone pls help a stressed student out

                  juliarobertsxxx Voltaic cells are electrochemical cells that convert chemical energy to electrical energy. Most of the time, VCAA wants to see the term “galvanic cell” since that’s the more common name for it. Primary and secondary cells are types of galvanic cells (primary = non rechargeable, secondary = rechargeable), whereas fuel cells are special galvanic cells that only work while the fuel is being supplied.

                  Electrolytic cells are electrochemical cells that use electrical energy to produce a chemical species through a non spontaneous reaction. When a secondary cell is being recharged, it’s an electrolytic cell

                    3 months later

                    Hi, this is related to subject selections but I wanted to know if it is it possible to take VCE Chem without prior exposure to it?
                    I didn't take subjects like Environmental Science or Investigations but I was hoping to take Chem for Yr 11 but I'm worried that I'm already behind considering it is a very hard subject.
                    I took only took Proj and Forensics this year so my Chem understanding is very minimal.

                      c:_melly If you have an interest in Chemistry and the motivation to apply yourself, I would say go for it! That's what Year 11 Chemistry is for, familiarising you with the basic concepts before going into Year 12.

                          GreenAcorn Thank you so much for the encouragement, I'm feeling a little more at eased now. (*´∀人) Thanks~

                            2 months later

                            hi, i'm doing wace chem but i have a question that hopefully can be answered - what are random errors and what are systematic errors? i've been struggling to find an answer that can differentiate between the two. can examples of these errors in the lab also be provided?

                            thanks in advance 🙂

                              juliarobertsxxx
                              Hi there,

                              Random errors are as a result of unpredictable variations in readings. They can be caused by estimating readings between lines on a measuring instrument (e.g. a measuring cylinder), or fluctuations during measuring (e.g. a draught through the room which changes the reading shown by an electronic balance). Random errors reduce precision of results as they increase the spread of readings. To reduce the effect of random errors, you can average your results, take more measurements or have a larger sample size.

                              Systematic errors are as a result of identifiable causes. They can be caused by incorrect calibration of measuring instruments, poorly maintained instruments, faulty readings by the user (e.g. parallax error when using a measuring cylinder). Systematic errors reduce accuracy of results as they shift measurements in one direction from the true value. To reduce the effect of systematic errors, you can correctly use the appropriate, calibrated equipment. Repeating an experiment won't reduce the effect of systematic errors.

                              Hope that helps!

                                a year later

                                hello I have no clue if this thread is still alive, but I have a few questions on fuel cells

                                • when it comes to the name of a fuel cell, what does that tell you?
                                  Once it said: phosphoric acid fuel cell, but that wasn't the substance which was a reactant, and another time it said ethanol fuel cell, which was a reactant.

                                Need help to understand how to approach " article based SAC for chemistry". Any guidance and mocks?

                                Write a Reply...