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Questions in chemistry

[Terjawab] Which substance has [tex]$\Delta H f$[/tex] defined as [tex]$0 kJ / mol$[/tex] ? [tex]$H _2 O$[/tex] (s) Ne (i) [tex]$F _2(g)$[/tex] [tex]$CO _2(g)$[/tex]

[Terjawab] 3. Petroleum is found in the purest form under the Earth's crust. 4. Oxygen gas is produced when coal burns. 5. Coke is harder and denser than charcoal.

[Terjawab] Select the correct answer. In this reaction, what effect does a change in the concentration of substances have on the reverse reaction rate? [tex]CaCO_3(s) \rightleftharpoons CaO(g)+CO_2(g)[/tex] A. The rate of the reverse reaction increases with an increase in the concentration of [tex]CaCO _3(s)[/tex]. B. The rate of the reverse reaction increases with an increase in the concentration of [tex]CaO (g)[/tex] and [tex]CO _2(g)[/tex]. C. The rate of the reverse reaction decreases with a decrease in the concentration of [tex]CaCO _3(s)[/tex]. D. The rate of the reverse reaction decreases with an increase in the concentration of [tex]CaO (g)[/tex] and [tex]CO _2(g)[/tex] E. The rate of the reverse reaction increases with a decrease in the concentration of [tex]CaO (g)[/tex] and [tex]CO _2(g)[/tex].

[Terjawab] The chemical formula for cesium oxide is $Cs _2 O$. What is the charge of cesium? A. +1 B. +2 C. -1 D. -2

[Terjawab] 5.5 500 g of Al₂(SO₄)₃ is dissolved in 2 dm³ water. 5.5.1 Define the term concentration. (2) 5.5.2 Calculate the concentration of the solution. (4)

[Terjawab] If the products of a reaction are $CO _2$ and $2 H _2 O$, what is known about the reactants? A. The reactants include $CO _2$ and $H _2 O$. B. The reactants include substances with only $C , O$, and H atoms. C. The reactants do not include any $C , O$, or H atoms. D. The reactants are also $CO _2$ and $H _2 O$.

[Terjawab] Select all the correct answers. Which statements correctly match a chemical name with its formula? Use the list of polyatomic ions and the periodic table to help you answer. A. The chemical formula for ammonium carbonate is $NH_4HCO_3$. B. The chemical formula for ammonium hypochlorite is $NH_4ClO$. C. The chemical formula for ammonium nitrate is $NH_4NO_3$. D. The chemical formula for ammonium phosphate is $NH_4(PO_4)_3$. E. The chemical formula for ammonium sulfate is $(NH_4)_2SO_3$.

[Terjawab] Which substance has [tex]$\Delta H f$[/tex] defined as [tex]$0 kJ / mol$[/tex] ? [tex]$H _2 O ( s )$[/tex] Ne (l) [tex]$F _2(g)$[/tex] [tex]$CO _2(g)$[/tex]

[Terjawab] Which of the following materials are irritants? A. Caustic soda B. Ethylene oxide C. Ethylbenzene D. Dichloromethane or "DCM" E. Turpentine

[Terjawab] Which of the following is the best definition of a physical change? A. A change in a substance with no new substances being formed B. A change in a substance in which mass is conserved C. A change in a substance where a new substance is formed D. A change in a substance in which bonds are broken