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Questions in chemistry

📝 Answered - What is the final chemical equation from the following intermediate chemical equations? [tex] \begin{array}{l} P_4 O_6(s) \rightarrow P_4(s)+3 O_2(g) \ P_4(s)+5 O_2(g) \rightarrow P_4 O_{10}(s) \end{array} [/tex]

📝 Answered - Which best describes an element? A. a pure substance B. a type of a mixture C. a pure compound D. an impure substance

📝 Answered - Complete combustion of a 0.350 g sample of a compound in a bomb calorimeter releases 14.0 kJ of heat. The bomb calorimeter has a mass of 1.20 kg and a specific heat of [tex]$3.55 J /\left( g ^{\circ} C \right)$[/tex]. If the initial temperature of the calorimeter is [tex]$22.5^{\circ} C$[/tex], what is its final temperature? Use [tex]$q=m C_p \Delta T$[/tex]. A. [tex]$19.2^{\circ} C$[/tex] B. [tex]$25.8^{\circ} C$[/tex] C. [tex]$34.2^{\circ} C$[/tex] D. [tex]$72.3^{\circ} C$[/tex]

📝 Answered - Which of these is an example of a physical change? A. A banana ripening in the air B. Hydrogen burning in the air C. Zinc reacting with an acid D. Liquid water turning into vapor

📝 Answered - A sample of octane [tex]$\left( C _8 H _{18}\right)$[/tex] that has a mass of 0.750 g is burned in a bomb calorimeter. As a result, the temperature of the calorimeter increases from [tex]$21.0^{\circ} C$[/tex] to [tex]$41.0^{\circ} C$[/tex]. The specific heat of the calorimeter is [tex]$1.50 J /\left( g \cdot{ }^{\circ} C \right)$[/tex], and its mass is 1.00 kg. How much heat is released during the combustion of this sample? Use [tex]$q=m C_p \Delta T$[/tex]. A. 22.5 kJ B. 30.0 kJ C. 31.5 kJ D. 61.5 kJ

📝 Answered - The synthesis reaction to form boron hydride is: [tex]2 B( s )+3 H _2(g) \rightarrow B _2 H _2(g), \Delta H =+36 KJ$[/tex]. What is the enthalpy value for the manipulated reaction: [tex]$1 / 2 B_2 H _2(g) \rightarrow B ( s )+3 / 2 H _2(g)$[/tex] ? A. -18 KJ B. -36 KJ C. +18 KJ D. +72 KJ

📝 Answered - If you need to reverse the following reaction in order for it to be an intermediate reaction in a Hess's law problem, what would be the final value for the enthalpy of reaction you use for this intermediate reaction? $C_2 H_4+3 O_2 \rightarrow 2 CO_2+2 H_2 O, \Delta H=-1410 kJ$ A. -1410 kJ B. -2820 kJ C. 2820 kJ D. 1410 kJ

📝 Answered - What would the final boiling point of water be if 3 mol of NaCl were added to 1 kg of water ( [tex]K_{ b }=0.51^{\circ} C /( mol / kg )[/tex] for water and [tex]i=2[/tex] for NaCl )? A. [tex]101.53^{\circ} C[/tex] B. [tex]98.47^{\circ} C[/tex] C. [tex]103.06^{\circ} C[/tex] D. [tex]96.94^{\circ} C[/tex]

📝 Answered - A complete combustion of a hydrocarbon forms 1.10 g of CO2 and 0.45 g of H2O. The molar mass of the hydrocarbon is 84.0 g mol⁻¹. Determine its empirical and molecular formula.

📝 Answered - Name the components of talcum powder. Answer the following questions in detail.