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Questions in chemistry

[Done] Which statement is true about this reaction? N+H-150 A. It is a practical source of energy on Earth. B. It occurs only outside the solar system. C. Its product is heavier than each of its reactants. D. It shows the critical mass of an element.

[Done] Q6. Rahim found three old chemical bottles in the storeroom of his house. He wants to test whether these chemicals are acidic, basic or neutral. Which of the following indicators should he use to test the chemicals? (a) Beetroot juice (b) Turmeric strip (c) Vanilla essence (d) China rose

[Done] Ammonia, [tex]$NH _3(\Delta H_1=-45.9 kJ)$[/tex], reacts with oxygen to produce water [tex]$\left(\Delta H_1=-241.8 kJ\right)$[/tex] and nitric oxide, [tex]$NO \left(\Delta H_1=\right.$ 91.3 kJ )[/tex], in the following reaction: [tex]$4 NH_3(g)+5 O_2(g) \rightarrow 6 H_2 O(g)+4 NO(g)$[/tex] What is the enthalpy change for this reaction? Use [tex]$\Delta H_{\text {rxn }}=\sum\left(\Delta H_{\text {t, products }}\right)-\sum\left(\Delta H_{\text {f, reactants }}\right)$[/tex]. A. -902 kJ B. -104.6 kJ C. 104.6 kJ D. 900.8 kJ

[Done] What is the mass percent of oxygen $( O )$ in $SO _2$ ? A. $\frac{(16.0 g+16 g)(6.02 \times 10^{23})}{100 g}$ B. $\frac{32.1 g}{16.0 g+16.0 g} \times 100 \%$ C. $\frac{16.0 g}{(32.1 g+16.0 g+16.0 g)} \times 100 \%$ D. $\frac{(16.0 g+16.0 g)}{(32.1 g+16.0 g+16.0 g)} \times 100 \%$

[Done] How does solubility for a solid vary with temperature? Some sample data similar to the lab is given below. Oxygen in Water | Temperature (°C) | Concentration (mg solute/mL solvent) | |---|---| | 5 | 0.12 | | 15 | 0.10 | | 25 | 0.08 | | 45 | 0.06 | Sucrose in Water | Temperature (°C) | Concentration (g solute/ml solvent) | |---|---| | 10 | 1.95 | | 30 | 2.20 | | 50 | 2.60 | | 70 | 3.20 |

[Done] 1. The smallest independent particle that makes up all the matter. 2. Substances that can flow from one place to another. 3. The liquid obtained by dissolving a solute in a solvent. 4. The process by which a liquid changes into a solid on cooling. 5. State of matter having loosely packed molecules.

[Done] $\begin{array}{c} Al \left( NO _3\right)_3( aq ) \text { and } Na _3 PO _4( aq ) \\ Al \left( NO _3\right)_3( aq )+ Na _3 PO _4( aq ) \rightarrow AlPO _4(s) \\ \text { Molecular Equation } \\ Al ^3+( aq )+3 NO _3( aq )+3 Na ^3+( aq )+ PO _4{ }^{3-}( aq ) \\ \text { Complete Ionic Equation } \\ Al ^{3+}( aq )+ PO _4{ }^3 \\ \text { Net Ionic Equation } \\ \text { Spectator Ions }\end{array}$

[Done] Consider the intermediate chemical reactions: [tex] \begin{array}{ll} Ca(s)+CO_2(g)+\frac{1}{2} O_2(g) \rightarrow CaCO_3(s) & \Delta H_1=-812.8 kJ \\ 2 Ca(s)+O_2(g) \rightarrow 2 CaO(s) & \Delta H_2=-1.269 .8 kJ \end{array} [/tex] The final overall chemical equation is [tex]$CaO ( s )+ CO _2(g) \rightarrow CaCO _3(s)$[/tex]. When the enthalpy of this overall chemical equation is calculated, the enthalpy of the second intermediate equation A. is halved and has its sign changed. B. is halved. C. has its sign changed. D. is unchanged.

[Done] Calculate the standard entropy change for the following reaction: [tex]$N _2 O _4(g) \rightarrow 2 NO _{2(g)}$[/tex] Given that: Substance (Formula) | Molar entropies | [tex]$S ^{\circ}$[/tex] in J/K ---|---|--- [tex]$N _2 O _4$[/tex] | 304.2 | [tex]$NO _2$[/tex] | 240.0 |

[Done] Lexi is balancing equations. She is finding one equation to be very difficult to balance. Which explains how to balance the equation [tex]ZnSO _4+ LbCO _2+ ZnCO _3+ Li _2 SO _4[/tex]? A. One reactant and one product needs the coefficient 2. B. The products both need a 3 coefficient. C. The reactants both need a 2 coefficient. D. Atoms in the equation are mostly in balance.