Test de evaluare la Chimie, clasa a VII – a Masă atomică - mol de atomi. Învelișul electronic
2p. 1. Calculează masa atomică relativă a atomului de neon știind că este format
din trei izotopi în următoarele proporții:
2010Ne = 89,97%; 2110Ne = 0,76%; 2210Ne = 9,27%
2p. 2. Ce masă au 2 moli de atomi de Cu, respectiv 2 moli de atomi de Fe? Se
dau: AFe = 56; ACu = 64
2p. 3. Calculează câți moli se găsesc în 50g de: a) carbon; b)sulf; c) calciu; d)
sodiu Se dau: AC = 12, AS = 32, ACa = 40, ANa = 23
2p. 4. Modelează structura învelișului electronic pentru:
Z=16S; Z=12Mg; Z=13Al; Z=10Ne

One or more substances changing into one or more substances is an example of a

Salicylic acid is a very important acid. it is used to synthesize the aspirin by treating with acetic anhydride. a 0.2015-g sample of salicylic acid was dissolved in a 100.00-ml volumetric flask, and the solution was diluted to the mark. a 10-ml aliquot of this solution was titrated with standard naoh (0.01130 + 0.2% n) to a phenolphthalein faint pink color end point at 19.81 ml. (a) (calculate the normality of the salicylic acid solution used in the titration. (b) assuming the salicylic acid is pure, what is the equivalent weight of the salicylic acid? practice problems for the final exam (continued) (c) (calculate the inherent error in the determination of the equivalent weight you calculated in part (b). use the following absolute errors in the equipment /glassware when calculating the inherent error. 5.00-ml pipet: + 0.02 ml 100-ml volumetric flask: + 0.08 ml analytical balance: + 0.2 mg 25-ml buret: + 0.03 ml

In an exothermic reaction the bonding energy of the product is: less than the reactants same as the reactants greater than the reactants dependent upon the presence of a catalyst