answer:
not positive if this is correct just what i ould find on google
The answer is "A. a pure substance can be separated by chemical means, while a mixture can be separated by physical means". A pure substance only has one type of substance, whereas a mixture has more than one. A pure substance therefore, can only be separated chemically, because it is not two things mixed together, whereas a mixture can be separated physically because there are multiple substances.
Atoms are the smallest particles of an element that can take part in a chemical reaction. During any chemical reaction no particles are created or destroyed: the atoms are simply rearranged from the reactants to the products. The products may have different properties to the reactants.
Mass is never lost or gained in chemical reactions. We say that mass is always conserved. In other words, the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning.
This fact allows you to work out the mass of one substance in a reaction if the masses of the other substances are known.
Answer:
6.517.
Explanation:
- It is known that for pure water: [H₃O⁺] = [OH⁻], so water is neutral.
<em>Kw = [H₃O⁺][OH⁻] = 9.25 x 10⁻¹⁴.</em>
∵ [H₃O⁺] = [OH⁻].
∴ [H₃O⁺]² = 9.25 x 10⁻¹⁴.
∴ [H₃O⁺] = √(9.25 x 10⁻¹⁴) = 3.041 x 10⁻⁷ M.
∵ pH = - log[H₃O⁺]
<em>∴ pH</em> = - log(3.041 x 10⁻⁷) = <em>6.517.</em>
