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Questions in chemistry

[Terjawab] When using chemicals, such as coil cleaner, the technician should always do which of the following? A. Review chemical Material Safety Data Sheet (MSDS) B. Wear skin protection C. All answers presented D. Wear safety goggles

[Terjawab] B. Name the separation method for the following: 1. Salt from sea water 2. Oil from water 3. Tea leaves from tea 4. Cream from milk 5. Wheat grains from husk

[Terjawab] Which statement best describes balancing equations and the law of conservation of mass? A. There are more atoms in the reactants than in the products, and the total mass is the same in the reactants and in the products. B. The number of atoms is the same in the reactants and in the products, and the total mass is the same in the reactants and in the products. C. There are fewer atoms in the reactants than in the products, and the total mass is less in the reactants than in the products. D. There are more atoms in the reactants than in the products, and the total mass is higher in the reactants than in the products.

[Terjawab] Magnesium metal reacts with dilute hydrochloric acid to produce magnesium chloride and hydrogen. The chemical equation for the reaction is shown below. [tex]Mg(s)+2 HCl(aq) \longrightarrow MgCl_2(aq)+H_2(g)[/tex] Starting with the known mass, 12.0 g of Mg, calculate the following: (a) the mass of HCl reacted, (b) the mass of [tex]MgCl_2[/tex] produced ([tex]Mg =24, Cl =35.5, H =1[/tex]).

[Terjawab] 12. Which of the following occur during the electrolysis of dilute H₂SO₄? A. The overall reaction is: H₂(g) + ½ O₂(g) → H₂O(g) B. SO₄²⁻ is discharged at the anode. C. A basic solution is formed. D. H⁺ is discharged at the negative electrode. 13. In an activity during laboratory session a small amount of lead bromide (PbBr₂) crystals were placed in a beaker. Two electrodes are inserted until they are in contact with the PbBr₂ crystals. When the PbBr₂ crystals in the beaker are gently heated, which of the following will be observed? A. Bromide ion is oxidized at the cathode. B. Bromine gas is evolved at the anode. C. Lead (II) ion is oxidized at the cathode. D. Lead (II) ion is reduced at the anode. 14. What is the name given to the pollution caused by the dumping of non-biodegradable wastes into the environment? A. Land pollution B. Air pollution C. Water pollution D. Sound pollution 15. What is the purpose of the conversion of pig iron to steel? A. To remove impurities by reduction. B. To remove impurities by oxidation. C. To decrease the concentration of iron in the pig iron. D. To increase the concentration of iron in the pig iron. 16. Which of the following statements CORRECTLY describes the law of conservation of mass? A. Mass is neither created nor destroyed during a chemical reaction. B. The total mass of substances varies during a chemical reaction. C. Pure compounds always contain the elements in the same percentage by mass. D. A particular compound is composed of the same elements in the same parts by mass.

[Terjawab] Sulfur reacts with oxygen to form sulfur dioxide ($SO_2(g), \Delta H_{f}=-296.8 \text{ kJ/mol}$) according to the equation below: $S(s)+O_2(g) \rightarrow SO_2(g)$ What is the enthalpy change for the reaction? Use $\Delta H_{\text{rxn}} = \sum(\Delta H_{\text{f,products}}) - \sum(\Delta H_{\text{f,reactants}})$ A. -593.6 kJ B. -296.8 kJ C. 296.8 kJ D. 593.6 kJ

[Terjawab] 1. From the following ionic equations below, put a tick (✓) if there is a reaction taking place and a cross (X) if there is no reaction taking place. a. [tex]Zn ^{2+}( aq )+ Fe ( s ) \longrightarrow Fe ^{2+}(\frac{ aq }{ a })+ Zn ( s )[/tex] b. [tex]Mg ^{2+}( aq )+ Zn ( s ) \longrightarrow Zn ^{2+}( aq )+ Mg ( s )[/tex] c. [tex]Fe ^{2+}( aq )+ Zn ( s ) \longrightarrow Zn ^{2+}( aq )+ Fe ( s )[/tex] d. [tex]Pn ^{2+}( aq )+ Cu ( s ) \longrightarrow Cu ^{2+}( aqu ) ! Pu ( s )[/tex] e. [tex]Cu ^{2+}( aq )+ Fe ( s ) \longrightarrow Fe ^{2+}( aq )+ Cu ( s )[/tex] 2. Define spectator ion

[Terjawab] The Lewis structures of four compounds are given. O=S=O O=C=O H-C(Cl)H-Cl Cl-P(Cl)-Cl Which of these molecules are polar? SO2 PCl3

[Terjawab] Scenario: You are testing two different household solutions with your cabbage indicator, using the color key to the right. Cabbage pH Indicator Color Key \begin{tabular}{l|l|l|l|l|}\0-2 & 3-4 & 5-6 & 7 & 8-9 \ \ \hline \end{tabular} Using the results from the two previous questions: Solution One: [tex]$1 \times 10^{-8} M$[/tex] Solution Two: [tex]$1 \times 10^{-7} M$[/tex] The hydrogen ion concentration of these two solutions differ from each other by a factor of

[Terjawab] Propane $(C_3 H_8(g), \Delta H_{ f }=-103.8 kJ / mol)$ reacts with oxygen to produce carbon dioxide $(CO_2, \Delta H_{ f }=-393.5 kJ / mol)$ and water ($H_2 O , \Delta H_f=-241.82 kJ / mol$) according to the equation below. $C_3 H_8(g)+5 O_2(g) \rightarrow 3 CO_2(g)+4 H_2 O(g)$ What is the enthalpy of combustion (per mole) of $C_3 H_8(g)$ ? Use $\Delta H_{\text {pxn }}=\sum(\Delta H_{\text {t, products }})-\sum(\Delta H_{\text {t, reactants }})$. A. $-2,044.0 kJ / mol$ B. $-531.5 kJ / mol$ C. $531.5 kJ / mol$ D. $2,044.0 kJ / mol$