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Questions in chemistry

[Homework Help] For each pair of gases, select the one that most likely has the highest rate of effusion. Use the periodic table if necessary. Oxygen $(O_2)$ or hydrogen $(H_2)$ : $ Methane $(CH_4)$ or carbon tetrachloride $(CCl_4)$ : $ Nitrogen $(N_2)$ or ammonia $(NH_3)$ : $ Fluorine $(F_2)$ or chlorine $(Cl_2)$ : $

[Homework Help] Draw a structural formula for the following: a. CH4 b. NaCl c. O₂ d. H₂O

[Homework Help] A cube of iron ([tex]$C_p=0.450 J / g \cdot{ }^{\circ} C$[/tex]) with a mass of 55.8 g is heated from [tex]$25.0^{\circ} C$[/tex] to [tex]$49.0^{\circ} C$[/tex]. How much heat is required for this process? Round your answer to three significant figures. Use the formula [tex]$q=m C_p \Delta T$[/tex].

[Homework Help] Two representative elements, nitrogen and oxygen, are in the same period of the periodic table. Which statement correctly describes the atoms of the two elements? A. They have the same number of valence electrons. B. They have valence electrons in different energy levels. C. They have the same number of electrons. D. They have valence electrons in the same energy level.

[Homework Help] How many kPa are in $2,150 mmHg$?

[Homework Help] This data set was created from examining several ice cores drilled at Antarctica's Vostok Station in 2001. Examine the data and write about one correlation that you see. What does the correlation tell you about Earth's historic atmosphere or climate? ($ybp =$ years before present, $ppb =$ parts per billion, and ppm = parts per million) | Depth (m) | Age (ybp) | Methane (ppb) | Carbon Dioxide (ppm) | Temperature Change from Current (${ }^{\circ} C$) | | --------- | --------- | ------------- | ------------------ | ------------------------------------------------- | | 355.765 | 9169 | 664.7 | 263 | 0.48 | | 362.915 | 9397 | 673.7 | 265.7 | 0.57 | | 374.57 | 9761 | 676.3 | 267.6 | 0.64 | | 381.715 | 9985 | 678 | 265.3 | 0.9 | | 389.97 | 10248 | 688 | 264 | 1.08 | | 399.215 | 10548 | 666 | 253.9 | 0.675 | | 407.43 | 10820 | 703 | 245.3 | 0.28 | | 415.27 | 11084 | 664.7 | 237.5 | -0.115 | | 427.27 | 11513 | 467.7 | 238.3 | -0.74 | | 434.52 | 11817 | 462.3 | 237.6 | -0.805 | | 445.965 | 12368 | 627 | 238.6 | -0.51 | | 453.77 | 12766 | 661.7 | 228.5 | -0.475 | | 463.565 | 13249 | 618.7 | 225.2 | -0.82 | | 469.72 | 13551 | 611.7 | 221 | -1.04 | | 484.02 | 14226 | 461 | 214 | -1.19 |

[Homework Help] A chemist wants to calculate the amount of heat that is absorbed by a sample of copper as it is melted. Which constant should she use? A. [tex]$\Delta H_{\text {fus }}$[/tex] B. [tex]$-\Delta H_{\text {vap }}$[/tex] C. [tex]$\Delta H_{\text {vap }}$[/tex] D. [tex]$-\Delta H_{\text {fus }}$[/tex]

[Homework Help] A sample of tin [tex]$\left( Cp =0.227 J / g \cdot{ }^{\circ} C \right)$[/tex] is placed in a freezer. Its temperature decreases from [tex]$15.0^{\circ} C$[/tex] to [tex]$-10.0^{\circ} C$[/tex] as it releases 543 J of energy. What is the mass of the sample? Round your answer to three significant figures. Use the formula [tex]$q=m C_\gamma \Delta T$[/tex].

[Homework Help] Complete the table below using the drop-down menus. | Number of Protons | Number of Neutrons | Atomic Number | Mass Number | Element (symbol) | |---|---|---|---|---| | A | 7 | B | 15 | C | | D | E | 26 | 56 | F |

[Homework Help] Name two elements that have a single valence electron.