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Questions in chemistry

[Terjawab] Which of the following describes an endothermic reaction? A. [tex]$\Delta H_{f, \text { products }}=0$[/tex] B. [tex]$\Delta H_{ f }$, products $\ \textgreater \ \Delta H_{ f }$, reactants[/tex] C. [tex]$\Delta H_{ f }$, products $=H_{ f }$, reactants[/tex] D. [tex]$\Delta H_{ f }$, products $\ \textless \ \Delta H_{ f }$, reactants[/tex]

[Terjawab] Which one is a chemical change? (a) Evaporation of a liquid (b) Breaking of a brick (c) Burning of a candle (d) Moving of a wheel Chemical changes are (a) mostly irreversible (b) always reversible (c) always irreversible (d) mostly reversible Which one is not a physical change? (a) Dissolution of salt in water (b) Tearing a piece of paper (c) Melting of wax (d) Digestion of food During the dissolution of urea, heat (a) is evolved (b) is absorbed (c) does not change (d) none of these

[Terjawab] 7. Which of the following is a common solvent? A. ethanol B. water C. ether D. benzene 8. Select the correct answer in the following, which is involved in the definition of "like". A. The nature of the bonding B. Structure of solute C. Structure of solvent D. The nature of bonding, structure of solute and solvent

[Terjawab] Use the terms in the vocabulary box to fill in the blanks. Vocabulary box: Concentrated, Solution, Soluble, Insoluble, Water, Solvent, Solute, Homogeneous, Heterogeneous, Solution. 17. Homogeneous solution means to have the uniform or the same appearance. 18. While the _______ mixture means that different substances are mixed and are visible. 19. A mixture of two or more substances that is homogeneous is called _______. 20. The _______ is the larger part of the solution. 21. While the smaller part is what we call _______. 22. A solution that can easily dissolve in one another is _______. 23. And if the liquids are not soluble, they are called _______ solution. 24. A _______ is a solution that contains a large amount of solute relative to the amount that could dissolve. 25. Finally, the _______ is considered as the universal solvent for it can dissolve almost any solute.

[Terjawab] In decarboxylation of sodium butanoate at STP, 5600 mL of CO₂ gas is liberated. Calculate the moles of CO₂ liberated at STP.

[Terjawab] Using the information in the table, calculate the enthalpy of combustion of 1 mole of acetylene for the reaction: [tex]2 C_2 H_2 + 5 O_2 \rightarrow 4 CO_2 + 2 H_2 O[/tex] | Compound | [tex]\Delta H _{ f } (kJ/mol)[/tex] | | :------------------------- | :------------------------ | | methane ([tex]CH_4[/tex]) | -74.8 | | acetylene ([tex]C_2 H_2[/tex]) | 226.8 | | ethanol ([tex]C_2 H_6 O[/tex]) | -235.1 | | carbon dioxide ([tex]CO_2[/tex]) | -393.5 | | water ([tex]H_2 O[/tex]) | -241.8 |

[Terjawab] Which term describes a pure substance that is made up of only one type of atom? A. matter B. rock C. compound D. element

[Terjawab] The mass of 0.5 mole of nitrogen gas is: (1) greater than the mass of 0.5 mole of nitrogen atoms (2) less than the mass of 0.5 mole of nitrogen atoms (3) is equal to the mass of one mole of nitrogen atoms (4) is equal to the mass of 0.5 mole of nitrogen atoms

[Terjawab] Which reaction is endothermic? $HCl + NaOH \rightarrow NaCl + H _2 O +58 kJ$ $6 CO _2+12 H _2 O +$ energy $\rightarrow C _6 H _{12} O _6+6 O _2+6 H _2 O$ $2 Na + Cl _2 \rightarrow 2 NaCl +$ energy $2 C _2 H _6+7 O _2 \rightarrow 4 CO _2+6 H _2 O +2,502 kJ$

[Terjawab] 4. Compare LPG and wood as fuels. 5. Give reasons. (a) Water is not used to control fires involving electrical equipment. (b) LPG is a better domestic fuel than wood. (c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.