Question 13 (1 point) \( \begin{array}{l}\text { Hydrogen sulphide gas can be deadly when in concentrations above } 650 \text { PPM (parts } \\ \text { per million). Express this value as a percentage. }\end{array} \)

d) \( \mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}+\mathrm{O}_{2} \rightarrow \quad \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} \)

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

Question 12 (1 point) \( \begin{array}{l}\text { 4) Listen } \\ \text { Medium carbon steel has a carbon content of } 0.35 \% \text {. What is the fractional portion } \\ \text { of carbon in this steel? }\end{array} \).

2. Determine el número de oxidación del elemento indicado en cada una de las sustancias siguientes: a) Ti en \( \mathrm{TiO}_{2} ; \) b) Sn en \( \mathrm{SnCl}_{4} ; \) c) C en \( \mathrm{C}_{2} \mathrm{O}_{4}^{2-} ; \) d) N en \( \left(\mathrm{NH}_{4}\right) \mathrm{SO}_{4} ; \) e) N en \( \mathrm{HNO}_{2} ; \) f) Cr en \( \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-} \)

b) qual é o número de valência dos elementos?