The half-life of Palladium-100 is 4 days. After 20 days a sample of Palladium-100 has been reduced to a mass of 1 mg . What was the initial mass (in mg ) of the sample? What is the mass 8 weeks after the start?

Which of the following element combinations will likely form polyatomic ions? oxygen and carbon cesium and chlorine sodium and bromine xenon and neon

How many grams are there in each of the following samples? (convert mols to grams) a. 3 mols of Beryllium-9

SECTION 3: Balance the following chemical reactions. a. \( \frac{\mathrm{Zn}}{\mathrm{Zinc}+\underset{\text { Hydrochloric Acid }}{\mathrm{HCl}} \rightarrow \underset{\mathrm{Zinc}}{\mathrm{ZnCl}}+\frac{\mathrm{H}_{2}}{\text { Chloride }}+\text { Hydrogen gas }} \)

4. How many atoms are found in a 15.3 g sample of bismuth? A. \( 1.26 \times 10^{26} \) atoms B. \( 4.41 \times 10^{22} \) atoms C. \( 6.02 \times 10^{23} \) atoms D. \( 9.21 \times 10^{24} \) atoms

\( \begin{array}{l}\text { Gas nitrogen dioksida }\left(\mathrm{NO}_{2}\right) \text { dapat membentuk gas } \\ \text { dinitrogen tetroksida }\left(\mathrm{N}_{2} \mathrm{O}_{4}\right) \text { dalam kesetimbangan } \\ \text { sebagai berikut: } \\ 2 \mathrm{NO}_{2}(\mathrm{~g})=\mathrm{N}_{2} \mathrm{O}_{4}(\mathrm{~g}) \\ \text { Jika pada suatu suhu diketahui konsentrasi } \mathrm{NO}_{2}= \\ 0,2 \mathrm{M} \text { dan } \mathrm{N}_{2} \mathrm{O}_{4}=0,5 \mathrm{M} \text {, tentukan nilai konstanta } \\ \text { kesetimbangan } \mathrm{Kc} \text { untuk reaksi tersebut. }\end{array} \).