Dobereiner's triads were an early attempt to sort the elements into some logical order by their physical properties. The appearance and reactions of the elements in a triad were similar to each other. He showed that in each triad the mean of the lightest and heaviest atomic weights approximated the atomic weight of the middle element.
Correct Answer: C<span>a(s) + 2H2O(ℓ) → Ca(OH)2(aq) + H2(g)
Reason:
A reaction (</span>transmutation) is said to be spontaneous if it occurs on it's own, without any external stimulus. For spontaneous reaction, change in free energy (ΔG) is negative.
Among the given reactions, Ca(s) + 2H2O(ℓ) → Ca(OH)2(aq) + H2(g) occurs on its own with supplying external energy. Hence, it is a spontaneous reaction. Further, it is an exothermic reaction. So during the reaction heat is given out by the system.
On other hand, reaction: <span>2KClO3(s) → 2KCl(s) + 3O2(g) is a decompostion reaction. For occurrence of reaction, heat has to be supplied to system. Hence, this reaction is non-spontaneous in nature. </span>
The solubility of a substance in water is dependent on the temperature. Thus for
1 & 2: Temperature is the independent variable (the one that changes in the first place) and Solubility is a dependent variable (a variable that changes in response to changes in the independent variable.)
The graph: by convention you shall label the horizontal axis with the independent variable and the vertical axis with the dependent variable. For clarity's sake you shall use the finest scale possible that accommodates for all data provided for both axis. Plot the data points on the graph as if they are points on a cartesian plane.
My teacher made no detailed requirements on the phrasing on titles of solubility curve plots; however, like most other graphs in chemistry, the title shall specify the name of variables presented in this visualization. For instance, "the solubility of
under different temperatures" might do. You shall refer to your textbooks for such convention.
It is necessary to interpolate to find the solubility at a temperature not given in the table. Start by connecting all given data points with a smooth line; find the vertical line corresponding to temperature = 75 degree Celsius and determine the solubility at the intersection of the vertical line and the trend line. That point shall approximates the solubility of the salt at that temperature.