Perubahan Kimia Benar: Practice Quiz

Rusting of iron involves a chemical reaction that changes the composition of the metal. It results in the formation of a new substance, illustrating a true chemical change.

The formation of gas bubbles is a clear sign that a new substance is being produced through a chemical process. Physical changes, like melting or cutting, do not involve the creation of new substances.

Burning wood is a chemical change as it produces new substances like gases and ash. The other processes merely change the physical form of the material without changing its chemical composition.

Balancing a chemical equation requires that the number of atoms for each element is equal on both the reactant and product sides. This upholds the law of conservation of mass.

A color change coupled with gas production indicates that new substances are being formed, a hallmark of a chemical reaction. Physical changes, such as breaking or melting, do not create new substances.

The coefficient '2' indicates that 2 moles of hydrogen gas are involved in the reaction. Coefficients represent the relative number of moles of each substance in the balanced equation.

The law of conservation of mass states that the mass of the reactants equals the mass of the products in any chemical reaction. This is why chemical equations must be balanced.

A catalyst provides an alternative pathway with a lower activation energy, thereby increasing the reaction rate without being permanently altered. It is not consumed during the reaction.

When no coefficient is indicated, it is assumed to be 1. This means that 1 mole of carbon is involved in the reaction.

A chemical change results in the formation of one or more new substances with different properties. Physical changes do not alter the chemical composition of the substance.

State symbols provide information about whether each substance is a solid, liquid, gas, or in an aqueous solution. This helps in understanding the conditions under which the reaction occurs.

The balanced equation for forming sodium chloride is 2Na + Cl2 -> 2NaCl. This indicates that the correct coefficient for sodium is 2.

The law of conservation of mass dictates that mass cannot be created or destroyed in a chemical reaction. Therefore, the mass of the products must equal the mass of the reactants, which in this case is 50 grams.

Exothermic reactions release energy because the products are at a lower energy level than the reactants. The difference in energy is typically given off as heat.

The coefficient shows the relative number of molecules or moles for each substance in the reaction. It ensures that the equation obeys the law of conservation of mass.

The combustion of propane is balanced as C3H8 + 5O2 -> 3CO2 + 4H2O, which shows 1 mole of propane reacting with 5 moles of oxygen to produce 3 moles of carbon dioxide and 4 moles of water. This satisfies the conservation of atoms for carbon, hydrogen, and oxygen.

Dividing 246 grams by 122.5 g/mol gives approximately 2 moles of KClO3. According to the balanced equation, 2 moles of KClO3 produce 3 moles of O2, which corresponds to 96 grams (3 x 32 g/mol).

In a 1:1 stoichiometric reaction, the reagent present in the smaller amount limits the reaction. With 4 moles of A and 5 moles of B, reactant A is the limiting reagent.

A drop in temperature suggests that the reaction is absorbing heat from its surroundings, which is characteristic of an endothermic process. In contrast, exothermic reactions release heat, leading to an increase in temperature.

The emergence of color combined with the release of heat implies that a chemical transformation has occurred, forming new compounds. This is indicative of an exothermic chemical change rather than a mere physical alteration.