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Questions in chemistry

[Free] What statement best describes the pattern of valence electrons seen on the periodic table? A. The number of valence electrons increases across a period from left to right, and the valence shell number decreases from top to bottom. B. The number of valence electrons decreases across a period from left to right, and the valence shell number decreases from top to bottom. C. The number of valence electrons decreases across a period from left to right, and the valence shell number increases from top to bottom. D. The number of valence electrons increases across a period from left to right, and the valence shell number increases from top to bottom.

[Free] Which statement best describes the compressibility of a gas? A. Increasing the temperature of a gas decreases the pressure. B. Increasing the temperature of a gas increases the pressure. C. Increasing the pressure on a gas decreases the volume. D. Increasing the pressure on a gas increases the volume.

[Free] Which substance absorbs 58.16 kJ of energy when 3.11 mol vaporizes? Use [tex]q=n \Delta H[/tex] \begin{tabular}{|r|r|r|} \hline [tex]H _2 O[/tex] & 6.01 & 40.7 \\ \hline [tex]CO _2[/tex] & 7.94 & 25.2 \\ \hline [tex]O _2[/tex] & 0.443 & 6.81 \\ \hline [tex]N_2[/tex] & 0.719 & 5.58 \\ \hline Fe & 14.9 & 354 \\ \hline Al & 10.7 & 255 \\ \hline Cu & 13.0 & 304 \\ \hline NaCl & 30.2 & 171 \\ \hline [tex]CH _4[/tex] & 0.936 & 8.53 \\ \hline [tex]H _2 S[/tex] & 2.37 & 18.7 \\ \hline \end{tabular}

[Free] In a chemistry lab, an unknown liquid boils at 148 K. What is its boiling point in degrees Fahrenheit? Include only the numerical value of your answer with a negative, if needed. This means, no units! Report with only one decimal place.

[Free] A scientist was studying an atom and through experimentation found that the total negative charge of the area surrounding the nucleus is -9. Which statement correctly describes this atom? A. This atom has nine clouds. B. This atom has nine electrons. C. This atom has nine neutrons. D. This atom has nine protons.

[Free] Which of the following is the source of potassium chloride? A. Animal B. Plant C. Mineral D. Human E. Synthesis

[Free] Use the drop-down menus to determine which state of matter is described in each statement. The atoms in a _____ are closely packed, but able to slide past each other. The atoms in a _____ spread as far apart as possible. A _____ has a definite shape and volume. The shape of a _____ can change, but the volume is definite.

[Free] Which valences have the greatest tendency to form ions? -2 +2 +4 +3 -3 -1 +1 -4

[Free] Which of the following is the source of barbiturates? A. Animal B. Plant C. Mineral D. Human E. Synthesis

[Free] If the pressure, volume, and temperature of a gas are known, which can most likely be found by using the ideal gas law? A. the molar amount of the gas B. the partial pressure of the gas C. the standard temperature and pressure D. the molar mass