For which of the following activities might you want to hire a chemist?
Answer: D. testing a rock sample for gold content
Which of the following procedures involves a physical change in one of the substances?
Answer: C. separating a salt solution by evaporating the water
Ionic bonds are forces that hold together electrostatic forces of attractions between oppositely charged ions. Ionic bonds have an electronegativity difference greater than or equal to 2. Covalent bonds have an electronegativity difference that is less than 2.
An energy profile of a reaction tells you whether it's endothermic or exothermic, the energy of the products and reactants, the activation energy needed for the forward (Ea) and reverse (Ea') reactions, the change in energy (∆E), and the energy of the activated complex.
Answer:
1) combustion
2) double replacement
3) combination
4) combustion
Explanation:
The combustion of a compound refers to the reaction of that compound with oxygen to produce heat and light. In reactions (1) and (4) above, ethanol and methane reacted with oxygen to yield carbon dioxde and water. This is a combustion reaction.
Reaction(2) is a double replacement reaction because the both cations exchange their anion partners in the product.
Reaction (3) is a combination reaction. It involves the joining of two elements to form a new compound.
