Which ones are true?
1. Combustion reactions are always endthermic
2. Exothermic reactions are reactions that absorb heat from the surroundings.
3. The products of combustion reactions are water and carbon dioxide.
I don't like any of the answers.
#1 definitely is not true.
#2 definitely is not true.
#3 probaby is the correct one for the author of the problem but it isn't true every time. For example, if I am combusting a hydrocarbon then yes, the products are CO2 and H2O. However, if I'm combusting H2 gas, then the product is H2O in this reaction. 2H2 + O2 ==> 2H2O
There are many examples of combustion that do NOT involve hydrocarbons.
To determine which statements are true, let's analyze each statement one by one:
1. Combustion reactions are always endothermic: This statement is not true. Combustion reactions can be classified as either exothermic or endothermic, depending on the reactants and conditions. In an exothermic combustion reaction, heat is released, while in an endothermic combustion reaction, heat is absorbed.
2. Exothermic reactions are reactions that absorb heat from the surroundings: This statement is incorrect. Exothermic reactions are actually reactions that release heat to the surroundings, resulting in an increase in the temperature of the surroundings. Heat is a product of the reaction, not something that is absorbed.
3. The products of combustion reactions are water and carbon dioxide: This statement is generally true for hydrocarbon combustion reactions. When a hydrocarbon (a compound made up of carbon and hydrogen) combusts, it reacts with oxygen to produce carbon dioxide and water vapor as the primary products. However, it is important to note that combustion reactions involving different compounds may produce different products.
To summarize, statement 3 is generally true, while statements 1 and 2 are false.