A simple composite scheme is presented and benchmarked against the 38 reactions in Truhlar's HTBH38/08 and NHTBH38/08 databases. Mean unsigned deviation (MUD) for the complete set of 68 independent barriers is 0.40 kcal mol À1 , compared to 1.31 kcal mol À1 for G4 and 1.62 kcal mol À1 for the M06-2X-D3 method. The MUD of the new scheme on the barriers in the DBH24/08 subset (12 out of the 38 reactions in the other sets) is 0.27 kcal mol À1 , better than that obtained at the expensive CCSD(T,full)/aug-cc-pCV(T+d)Z level (0.46 kcal mol À1 ) and comparable to the most exact (and costly) Wn calculations (MUD = 0.14 kcal mol À1 ). The method was further tested against a subset of reactions, for which the geometry and energies of all species were determined at the much more demanding CCSD(T)-F12//pVQZ-F12 level. The SVECV-f12 procedure on this database results in RMSE and MUD values of only 0.21 and 0.16 kcal mol À1 .
As a fundamental part of their chemical education, first-year undergraduate students are substantially involved in laboratory activities. Despite the specific teaching staff choices on the main laboratory aims, students normally receive a vast amount of information during these activities. Apart from understanding theoretical content, fundamental skills such as manipulation, data collection and interpretation should be developed. In this context, learners could feel overwhelmed since they can only process a few pieces of information at a time. Indeed, our experience at theUniversidad de la República(Uruguayan public university) shows that many first-year students are in fact not able to cope with all the information they receive during laboratory activities. As a result, many of them only follow the experimental protocol automatically, without gaining significant knowledge or developing the necessary skills. In this work, we assessed the use of new online interactive pre-laboratory activities implemented for 252 first-year university students enrolled in a 12-module General Chemistry laboratory course. The student choice of interactiveversusmore traditional material was evaluated together with observed preferences regarding the different interactive tools offered. Besides, an online pre-laboratory discussion forum was also implemented and assessed. Both the interactive material and the discussion forum were chosen freely by the majority of students (61% and 79%, respectively). Interestingly, the choice was to some extent modulated by student previous performance. Interactive pre-laboratory material was more frequently chosen by low previous performance students, whereas pre-laboratory forum was preferentially used by high previous performance students. Finally, the influence of these new materials on student laboratory performance was statistically analyzed. Other personal and academic variables were also taken into account. Interactive material access was positively correlated with the final laboratory marks for medium previous performance learners. On the other hand, for lower previous performance students, the academic discussion between teachers and partners promoted by the online forum was positively correlated with their academic performance.
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