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Questions in chemistry

[Terjawab] A solid precipitate is formed from the reaction of lead nitrate and sodium chromate. What would be the best method to separate this solid from the solution? A. distillation B. evaporation C. filtration D. sorting

[Terjawab] Which of these materials is most effective against chemical hazards? A. Cloth B. Leather C. Rubber D. Mesh

[Terjawab] A balloon containing helium gas expands from 230 mL to 860 mL as more helium is added. What was the initial quantity of helium present if the expanded balloon contains $3.8 \times 10^{-4} mol$, assuming constant temperature and pressure? Use the formula: $\frac{V_1}{n_1}=\frac{V_2}{n_2}$ A. $1.0 \times 10^{-4} mol^6$ B. $1.5 \times 10^{-4} mol$ C. $1.0 \times 10^{-3} mol$ D. $1.4 \times 10^{-3} mol$

[Terjawab] 1. Choose the condition in which a silver cup will tarnish. A. Presence of sulphur in air and coated with oil B. Presence of oxygen in air and coated with oil C. Presence of sulphur in air and coated with water D. Presence of oxygen in air and coated with grease 2. Explain with an example why corrosion is a harmful chemical process and write 2 ways to prevent it. 3. Which place is likely to have a greater chance of corrosion - a place with 40% humidity or a place with 60% humidity? Give reasons for your answer.

[Terjawab] The fire tetrahedron includes fuel, heat, combustion (chemical reaction), and A. Aerosol B. Oxygen C. Carbon monoxide D. Gasoline

[Terjawab] The production of water proceeds according to the following equation: [tex]$2 H_2(g)+O_2(g) \rightarrow 2 H_2 O(g)$[/tex] Which describes a way to speed up the collisions between hydrogen and oxygen molecules to produce more water? A. Use a less-intense source of heat on the reactants. B. Maintain the same temperature of the reactants. C. Place the reactants in a smaller container. D. Reduce the concentration of the reactants.

[Terjawab] Which balances the equation $Mg + O _2 \rightarrow MgO$? A. $Mg +2 O _2 \rightarrow 4 MgO$ B. $2 Mg +2 O _2+2 MgO$ C. $2 Mg + O _2 \rightarrow 2 MgO$ D. $2 Mg +2 O _2 \rightarrow 4 MgO$

[Terjawab] Ammonia, [tex]$NH _3(\Delta H_{ f }=-45.9 kJ)$[/tex], reacts with oxygen to produce water ([tex]$\Delta H_{ f }=-241.8 kJ$[/tex]) and nitric oxide, [tex]$NO (\Delta H_{ f }=$[/tex] 91.3 kJ ), 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]$\Delta H_{r x n}=\sum(\Delta H_{f, \text { products }})-\sum(\Delta H_{f, \text { reactants }})$[/tex]. A. -902 kJ B. -104.6 kJ C. 104.6 kJ D. 900.8 kJ

[Terjawab] Element with the electron configuration $1 s^2 2 s^2 2 p^6 3 s^2 3 p^5$ is A. potassium B. fluorine C. sulfur D. chlorine E. carbon

[Terjawab] Activity 1 Which are Elements? Which are Compounds? Directions: Inside the box are the substances that are found in the cabinet. Identify the elements and compounds by accomplishing the table below. | IRON | SODIUM CHLORIDE (SALT) | SULFUR | CARBON | |---|---|---|---| | MAGNESIUM RIBBON | SUGAR | OIL | BAKING SODA | | COPPER | ALUMINUM | DISTILLED WATER | CHLORINE | | ELEMENTS | COMPOUNDS | |---|---| | | |