Rezolvati urmatoarele exercitii si probleme: 1. Alege varianta corectă: concentrația unei soluții (c =

md

ms

∙ 100), obținute prin dizolvarea a 40

g sare în 360 g apa este: a) 20 %,

b) 18 %,

c) 10 %.

2. Se amestecă 500 g soluție de saramură 20% cu 300 g soluție de saramură 50% și cu 200 g apă.

Să se calculeze concentrația soluției finale.

3. Alege, folosindu-te de SP, metalele si nemetalele din sirul de elemente: Hg, Cl, B, Ca, Na, Fe,

As, Fr, O, Mg

4. Aflati elementul chimic, stiind ca se afla in gr. IVA si perioada 3.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2

може ли да зареждате повече информация, моля

c

explanation: