Upon thermal decomposition of X, a black compound was expected, but a red compound was found instead, what might be the reason? (Exam 1 L2 Ch2) a) condition of (absence of air ) was not properly applied b) the temperature applied was not sufficient c) the wrong compound was thermally decomposed instead of the correct one d) both a and c are correct

Calculate the density of a cup of tap water at room temperature with a mass of 50.8 g and a volume of 52.1 mL . Round your answer to the appropriate number of sig figs. \( 0.975 \mathrm{~g} / \mathrm{mL} \) \( 1.0 \mathrm{~mL} / \mathrm{g} \)

13 gás hidrogênio reage com gás cloro produzin- do ácido clorídrico. Ao reagir 10 g de hidrogênio com 500 g de cloro, houve formação do produto ácido, mas observou-se que 145 g de cloro per- maneceram sem reagir. Qual será a massa, em gramas, do ácido clorídrico formado? Justifique

An iron ore ( X ), 2 elements ( \( Y \) and Z ) from this ore are used in making 2 types of alloys, if you know that element \( Y \) is a source of reducing agent in blast furnace, which of the following is true about element ( z ) and iron ore \( (\mathrm{X} \) ) respectively? (Exam \( 1 \mathrm{L2} \mathbf{C h} 2 \) ) a) \( Z \) has highest magnetic moment in oxidation state +2 , while \( X \) is paramagnetic b) \( Z \) has highest magnetic moment in oxidation state +3 , while \( X \) is thermally decomposed in air giving a black oxide c) \( Z \) is not considered as a transition element, while \( X \) is thermally decomposed in absence of air giving a black oxide d) \( Z \) forms paramagnetic compounds in most of it's oxidation states, while \( X \) requires roasting before reduction

3. Para las reacciones redox completas que se muestran a continuación: a) divida cada reacción en sus semirreacciones; b) identifique el agente oxidante; c) identifique el agente reductor. a) \( 2 \mathrm{Sr}+\mathrm{O}_{2} \rightarrow 2 \mathrm{SrO} \) b) \( 2 \mathrm{Li}+\mathrm{H}_{2} \rightarrow 2 \mathrm{LiH} \) c) \( 2 \mathrm{Cs}+\mathrm{Br}_{2} \rightarrow 2 \mathrm{CsBr} \) d) \( 3 \mathrm{Mg}+\mathrm{N}_{2} \rightarrow \mathrm{Mg}_{3} \mathrm{~N}_{2} \) e) \( 4 \mathrm{Fe}+3 \mathrm{O}_{2} \rightarrow 2 \mathrm{Fe}_{2} \mathrm{O}_{3} \) f) \( \mathrm{Cl}+2 \mathrm{NaBr}_{2} \rightarrow 2 \mathrm{NaCl}+\mathrm{Br}_{2} \) g) \( \mathrm{Si}+2 \mathrm{~F}_{2} \rightarrow \mathrm{SiF}_{4} \) h) \( \mathrm{H}_{2}+\mathrm{Cl}_{2} \rightarrow 2 \mathrm{HCl} \)

b) qual é o número de valência dos elementos?