Which best describes the total mass of substances before and after a combustion reaction? A. The mass is the same because the molecules do not change. B. The mass is the same because atoms are not created or destroyed. C. The mass is less after the reaction because gases are produced. D. The mass is greater after the reaction because the number of atoms increases.

8. A piece of zinc was added to \( 1000 \mathrm{~cm}^{3} \) of 0.2 M hydrochloric acid. After effervescence had stopped, \( 28 \mathrm{~cm}^{3} \) of the resulting solution required \( 17 \mathrm{~cm}^{3} \) of 0.08 M sodium trioxocarbonate(IV) solution for complete neutralization. Calculate the mass of the zinc added. \( \mathrm{Zn}=65, \mathrm{HCl}= \) \( 36.5 \mathrm{Na.CO}=106 \) )

renocarbonato de potassia fosfato de esloia, cianeto de curo (i) e sulfeto de sodio podem ser usador em banhos para douraslo esses compostos.

os nomes dos compostos químicos de fórmulas \( \mathrm{NH}_{4} \mathrm{NO}_{3} \mathrm{ePDI}_{2} \).

The half-life of the radioactive element unobtanium- 47 is 10 seconds. If 80 grams of unobtanium- 47 are initially present, how many grams are present after 10 seconds? 20 seconds? 30 seconds? 40 seconds? 50 seconds?

(Unesp) Escreva: a) as formulas químicas dos compostos hidrogenocarbonato de sódio e sulfato de ferro (III).