Endothermic reactions are reactions that proceed by the absorption of heat (energy) while exothermic reactions involve a release of energy.
a) Formation of frost on a car window in winter is an exothermic process as heat is liberated when liquid water freezes to form crystals
b) Formation of water condensate on a glass of ice water is an endothermic reaction since heat is absorbed by the cold water from the glass container thereby cooling it.
c) A decrease in the temperature as ammonium nitrate is added to water is an endothermic reaction
ANSWER
Option A
EXPLANATION
Arrhenius defines an acid as a substance that will produce hydrogen ions as the only positive ion when dissolved in water.
He also defines a base as a substance that contains a hydroxide ion (OH^-).
Hence, the Arrhenius Model of acids and bases applies that is applied to the aqueous solution.
The correct answer is option A
3.16 X 10^-11 M is the [OH-] concentration when H3O+ = 1.40 *10^-4 M.
Explanation:
data given:
H30+= 1.40 X 10^-4 M\
Henderson Hasslebalch equation to calculate pH=
pH = -log10(H30+)
putting the values in the equation:
pH = -log 10(1.40 X 10^-4 M)
pH = 3.85
pH + pOH =14
pOH = 14 - 3.85
pOH = 10.15
The OH- concentration from the pOH by the equation:
pOH = -log10[OH-]
10.5= -log10[OH-]
[OH-] = 10^-10.5
[OH-] = 3.16 X 10^-11 is the concentration of OH ions when hydronium ion concentration is 1.40 *10^-4 M.
Answer:
Explanation:
Compound
A compound contains atoms of different elements chemically combined together in a fixed ratio.
Compounds contain different elements in a fixed ratio arranged in a defined manner through chemical bonds. They contain only one type of molecule. Elements that compose the compound are chemically combined.
A compound can be separated into simpler substances by chemical methods/reactions.
A huge, virtually limitless, number of chemical compounds can be created. Compounds are classified into molecular compounds, ionic compounds, intermetallic compounds and complexes.
A compound is represented using its chemical formula that represents the symbols of its constituent elements and the number of atoms of each element in one molecule of the compound
Element
An element is a pure chemical substance made of same type of atom.
Elements contain only one type of atom. Each atom has the same atomic number i.e., the same number of protons in their nucleus.
Elements cannot be broken down into simpler substances by chemical reactions.
There are about 117 elements that have been observed. Can be classified as metal, non-metal or metalloid.
An element is represented using symbols.
