(b) Fill in the blanks. (i) Hydrogen is prepared in the laboratory by the reaction of hydrochloric acid. (ii) The number of shells is equal to the number of (iii) Arsine gas is an impurity present in hydrogen which can be removed by passing the gas (iv) Hydrough is not collected by the downward displacement of air, because it forms (v) Group with air.

(iii) Identify the metal which reacts both with acid and alkali to liberate hydrogen: a. Mg b. Zn c. Cu d. Ag

\begin{tabular}{l} 23. La escala de pH mide la acidez de una sustancia y la relacioria \\ con su concentraciôn de iones de hidrógeno c , medida en molitro, \\ mediante la siguiente igualdad: \\ \( \qquad \mathrm{pH}=-\log \mathrm{c} \) \\ Si la concentración de iones de hidrógeno de una infusión de té es \\ \( \mathrm{c}=4,1 \cdot 10^{-3} \) molitro, ¿qué expresion es igual a su pH ? \\ A \( 3 \log 4,1 \) \\ (B \( -3 \log 4,1 \) \\ C \( 3 \log 4,1+3 \) \\ D \( -\log 4,1+3 \) \\ \hline\end{tabular}

(i) State Mendeleev's periodic law.

\( P V=n R T \quad \) para \( R \)

At the beginning of an experiment, a scientist has 260 grams of radioactive goo. After 210 minutes, her sample has decayed to 8.125 grams. What is the half-life of the goo in minutes? Find a formula for \( G(t) \), the amount of goo remaining at time \( t \). \( G(t)= \)