JY CHEN - Ask Anything, Learn Everything. Logo

Questions in chemistry

[Free] The specific heat capacity of a pure substance can be found by dividing the heat needed to change the temperature of a sample of the substance by the mass of the sample and by the change in temperature. The heat capacity of a certain substance has been measured to be [tex]$3.08 \frac{J}{ g \cdot{ }^{\circ} C }$[/tex]. Suppose [tex]$350 . g$[/tex] of the substance are heated until the temperature of the sample has changed by [tex]$48.6^{\circ} C$[/tex]. Write an equation that will let you calculate the heat [tex]$Q$[/tex] that was needed for this temperature change. Your equation should contain only symbols. Be sure you define each symbol.

[Free] The heat of vaporization for water is $40.7 kJ / mol$. How much heat energy must 150.0 g of water absorb to boil away completely? Use the formula $q=n \Delta H$.

[Free] The table gives the data that is needed to calculate the average atomic mass of element B. | Isotope | Atomic mass (amu) | Relative abundance (%) | |---|---|---| | B-10 | 10.01 | 19.91 | | B-11 | 11.01 | 80.09 | Based on these data, what is the average atomic mass of element B? A. 10.5 B. 10.01 C. 11.01 D. 10.81

[Free] $\begin{array}{l}5.74 cm+0.823 cm+2.651 cm=9.214 cm=\ldots cm \\ 4.8 L-3.965 L=0.835 L=\ldots L \\ 5.02 nm \times 89,665 nm \times 0.10 nm=45,011.83 nm^3=\ldots nm ^3 \\ 5.892 g \div 6.10 mL=0.96590 g / mL =\ldots g / mL \end{array}$

[Free] Which chemical reaction involves the production of a gas? 1. [tex]2 Li ( s )+ F _2(g) \rightarrow 2 LiF ( s )[/tex] 2. [tex]Zn ( s )+2 HCl ( aq ) \rightarrow H _2(g)+ ZnCl _2( aq )[/tex] 3. [tex]HNO _3( I )+ H _2 O ( l ) \rightarrow H _3 O ^{+}( aq )+ NO _3{ }^{-}( aq )[/tex] 4. [tex]K _2 CrO _4( aq )+ Ba \left( NO _3\right)_2( aq ) \rightarrow BaCrO _4(s)+2 KNO _3( aq )[/tex]

[Free] A $1,628 g$ sample of a hydrate magnesium iodide is heated until its mass is reduced to $1,072 g$ and all water has been removed. What is the formula of the hydrate? (MgI $\cdot x_{ H _2 O }$ )

[Free] Collect data: Beginning with Na, record the number of energy levels, number of protons, and atomic radius for each element in period 3. | Element | Na | Mg | Al | Si | P | S | Cl | Ar | |---|---|---|---|---|---|---|---|---| | Number of energy levels | | | | | | | | | | Number of protons | | | | | | | | | | Atomic radius $(pm)$ | | | | | | | | |

[Free] A sample of water has a mass of 100.0 g. Calculate the amount of heat required to change the sample from ice at [tex]$-45.0^{\circ} C$[/tex] to liquid water at [tex]$75.0^{\circ} C$[/tex]. Use the chart to complete the multiple steps required to arrive at the final answer. Type in your answers below using 3 digits. [tex] \begin{array}{l} q_1=\square kJ \\ q_2=\square kJ \\ q_3=\square kJ \\ q_{tot}=\square kJ \end{array} [/tex] [tex]\begin{tabular}{|l|l|l|l|} \hline $\Delta T ( C )$ & Phase Chango & Constant & Formula \\ \hline $-45.0 \rightarrow 0.00$ & Warm solid & $C _{0.2003}= 2093 J / g ^{\circ} C$ & $q _1= cm \Delta T$ \\ \hline 0.00 & Melt solid & $\Delta H_{\text {max }}= 40.7 kJ / mol$ & $q _2= n \Delta H _{ kvs }$ \\ \hline $0.00 \rightarrow 75.0$ & Warm liquid & $C_{0.1024}= 4.184 J / g ^{\circ} C$ & $q _3= cm \Delta T$ \\ \hline $-45.0 \rightarrow 75.0$ & Sol $\rightarrow$ liq & & $q_{12}=q_1+q_2+q_3$ \\ \hline \end{tabular}[/tex]

[Free] Which substance is a strong electrolyte? $NH _3$ $Ba ( OH )_2$ $C _{12} H _{22} O _{11}$ $CH _3 COOH$

[Free] When working with chemicals, what two pieces of safety equipment will you be required to use? Which is correct: (1) The acid should be poured into water OR, (2) the water should be poured into the acid?