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1.Why some type of observations are particularly needed to determine whether a chemical reaction has taken place ?
2.Why most of the reactions are categorized as redox reactions?
3.Why most of the reactions are exothermic in nature?
4.In the electrolysis of water , one of the gases collected in test tubes more than other.Why is it so?
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HOMEWORK HELP > SCIENCE
What observations help us determine whether a chemical reaction has taken place?
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C67JULIE | CERTIFIED EDUCATOR
There are several observations that can be made to determine if a chemical reaction has occurred. The first is a change in temperature. Heat can be absorbed (endothermic reaction) or released (exothermic reaction) which results in a temperature change. This can be noted with a thermometer. Reactions can also have a color change. A change in color represents a chemical reaction. Another observation is if there is a smell or odor after the reaction takes place. When a reaction takes place, gases can sometimes be removed from the system. This can be observed by the formation of bubbles. Another observation is the formation of a precipitate. This is a solid that forms out of solution. When a solute is dissolved in a solution, a chemical reaction took place. Lastly, if there is a change in pH a chemical reaction took place. This will need to be tested with pH strips.
2. Redox reactions are classified by having both an oxidation reaction and a reduction reaction, and hence, an oxidizing agent and a reducing agent. ... When a change in oxidation number occurs in a reaction, with both an increase in number and a decrease in number, then the reaction is classified as redox.
3. Most of the reactions occur by releasing energy. That means all reactions occur by breaking of bonds in reactant and formation of product. ... Many reactionslike oxidation, combustion all occur by liberation of energy. Moreover the exothermic reactions are always spontaneous and the product produced are stable.
4. The chemical reaction involved in theelectrolysis of water is From the above reaction it is clear that the amount of hydrogen gas and the oxygengas formed are always in the ratio of 2:1. Therefore the volume of gas collected in the first test tube is double the volume of the gas collected in second test tube.
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