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Questions in chemistry

[Free] What is a compound? A. A substance made of one type of atom B. A mixture of different substances C. Two or more different elements chemically joined D. A solution of gases

[Free] Directions: Use the top part of the periodic table above to complete the table below. \begin{tabular}{|l|l|l|l|l|l|l|}\hline Element & Symbol & # of Protons & # of Neutrons & # of Electrons & Atomic Number & Atomic Mass \\ \hline Silicon & Si & 14 & 14 & 14 & 14 & 28.09 \\ \hline manganese & Mn & 25 & 30 & 25 & 25 & 54.94 \\ \hline Sodium & & & I & 11 & & 22.99 \\ \hline & & 6 & & 6 & & \\ \hline Beryllium & & & 5 & & & \\ \hline & & & & 8 & & \\ \hline & & 13 & & & & \\ \hline\end{tabular}

[Free] Calculate the amount of heat released when [tex]$27.0 g H _2 O$[/tex] is cooled from a liquid at 314 K to a solid at 263 K. The melting point of [tex]$H _2 O$[/tex] is 273 K. Using the chart below, complete the steps to calculate the overall heat released in the process. Type in your answers using 3 digits on the right. [tex]\begin{tabular}{|l|l|l|l|}\hline $\Delta T ( K )$ & Phase Change & Constant & Formula \\\hline $314 \rightarrow 273$ & Cool liquid & $C_{\text {p, lquid }}=4.184 J / g \cdot K$ & $q _1= cm \Delta T$ \\\hline 273 & Freeze liquid & $\Delta H_{\text {fusion }}=6.01 kJ / mol$ & $q _2= n \Delta H _{\text {fus }}$ \\\hline $273 \rightarrow 263$ & Cool solid & $C_{ p , \text { soluc }}=2.093 J / g \cdot K$ & $q _3= cm \Delta T$ \\\hline $314 \rightarrow 263$ & Liq $\rightarrow$ Sol & & $q_{\text {rot }}=q_1+q_2+q_3$ \\\hline\end{tabular}[/tex] [tex]\begin{array}{l} q_1=\square kJ \ q_2=\square kJ \ q_3=\square kJ \ q_4=\square kJ\n\end{array}[/tex]

[Free] Most semiconductors are found in what area of the periodic table? A. The representative elements. B. The carbon family, column 14 or IVA. C. Period 3 D. Column 18, or VIIIA

[Free] The incomplete table below shows a comparison of the different gas laws. \begin{tabular}{|l|l|l|l|} \hline Name & Variables & Constants & Equation \\ \hline Boyle's law & pressure, volume & ? & $P_1 V_1=P_2 V_2$ \\ \hline Charles's law & volume, temperature & ? & $\frac{V_1}{T_1}=\frac{V_2}{T_2}$ \\ \hline ? & temperature, pressure & volume, moles of gas & $\frac{P_1}{T_1}=\frac{P_2}{T_2}$ \\ \hline ? & pressure, temperature, volume & ? & $\frac{P_1 V_1}{T_1}=\frac{P_2 V_2}{T_2}$ \\ \hline \end{tabular} What is assumed to be constant when using the combined gas law? A. pressure B. number of moles C. volume and moles of gas

[Free] Which statement accurately describes the chemical symbol of an element? A. The chemical symbol is always a single letter. B. The chemical symbol always starts with the same letter as the name of the element. C. The chemical symbol always begins with a capital letter. D. The chemical symbol can be shared by more than one element.

[Free] Which statement is true regarding elemental and compound molecules? A) Elemental molecules contain different types of atoms. B) Compound molecules are made of the same type of atoms. C) Elemental molecules consist of two or more atoms of the same element. D) Compounds do not have a fixed composition.

[Free] Complete the table to describe each atom using the periodic table. Type in your answers. | Number of Protons | Number of Neutrons | Atomic Number | Mass Number | Element (symbol) | |---|---|---|---|---| | A | 7 | B | 15 | C | | D | E | 26 | 56 | F | A: B: C: D: E: F:

[Free] Using the information in the table to the right, calculate the average atomic mass of strontium. Report to two decimal places. | Isotope | Mass (amu) | Abundance | |---|---|---| | Sr-84 | 83.913428 | 0.56 % | | Sr-86 | 85.909273 | 9.86 % | | Sr-87 | 86.908902 | 7.00 % | | Sr-88 | 87.905625 | 82.58 % |

[Free] Which change would increase the pressure exerted by a gas? A. removing gas molecules from the container B. transferring the gas to a larger container C. raising the temperature of the gas D. reducing the force of the molecules hitting the container