Zadanie 6
Boron has two naturally occurring isotopes. A sample contains 20.0 % boron-10 () and 80.0 % boron-11 (). What is the relative atomic mass of boron in this sample? A. 10.2 B. 10.5 C. 10.8 D. 11.0
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Boron has two naturally occurring isotopes. A sample contains 20.0 % boron-10 () and 80.0 % boron-11 (). What is the relative atomic mass of boron in this sample? A. 10.2 B. 10.5 C. 10.8 D. 11.0
Which elements are metalloids? I. Silicon II. Antimony III. Bismuth A. I and II only B. I and III only C. II and III only D. I, II and III
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Sulfur dioxide, SO2, has sulfur as the central atom. The electronegativity of sulfur is 2.6 and that of oxygen is 3.4. Which row describes the polarity of the bonds and of the molecule correctly? A. S=O bonds: O is δ − and S is δ +;…
A pure metal is mixed with a small amount of a second metal whose atoms have a different radius. The regular arrangement of atoms is distorted, so the layers can no longer glide past one another easily. Which property of the metal will increase as a result? A.…
The average bond lengths of three carbon-halogen bonds are shown. What is the order of increasing bond strength? A. C−Cl < C−Br < C−I B. C−I < C−Br < C−Cl C. C−Br < C−I < C−Cl D.…
What is the enthalpy change of the reaction 2 C(s) + 3 H2(g) → C2H6(g), calculated from the enthalpy changes of the three reactions below? C(s) + O2(g) → CO2(g), ΔH = −394 kJ mol−1 ,…
Which statement about heat and temperature is correct? A. Temperature is a measure of the total energy transferred between particles B. Heat is a measure of the average kinetic energy of the particles in a sample C. Temperature is a measure of the total…
The graph shows how the concentration of a reactant changes with time. What initial rate of reaction, in mol dm−3 s−1, can be determined from the graph? A. 0.1 B. 0.2 C. 0.5 D. 2.0