Answer:
Explanation:
Phenolphthalein is a protonated indicator and methyl orange is a basic indicator having hydroxyl ionisable part .
Phenolphthalein can be represented by the following formula
HPh which ionizes in water as follows
HPh + H₂O ⇄ H₃O⁺ + Ph⁻
( colourless ) ( pink )
In acidic solution it is in the form of protonated Hph form which is colourless
In basic medium , it ionises to give H₃O⁺ and unprotonated Ph⁻ whose colour is pink .
Answer:
The geologist time scale was formed when scientists studied rock layers and index fossils worldwide. With this information, they placed Earth's rocks in order by relative age. Later, radioactive dating helped determine the exact age of the divisons in the geologic time scale.
This scale is organized by the 4.6 billion years of earth's history into sections based on important changes seen in the geologic record. The largest intervals are called eons, with each eon containing many millions of years.
In precambarian time the processes that affect Earth's surface have lessened the erosion on the surface. Earth was being hit by meteorites every second. Now there is water erosion and there wasn't back then. The surface changes have lessened over time.
Answer:
hydrochloric acid
Explanation:
The hydrochloric acid in this reaction is the limiting reactant. A limiting reactant is the reactant that is used up in a chemical reaction. It determines the extent of the reaction.
Since the solution indicates a basic one after the end of the reaction, this suggests that more of the sodium hydroxide is still left unreacted with.
The reactant in excess supply here is the sodium hydroxide and the bulk of it is till left in solution.
Answer:
B. Ca(NO2)2
Explanation:
Ions (charged atoms) combine with one another to form stable ionic compounds. In this case, calicium ion (Ca2+) is said to react with NO2, which has a charge of -1 i.e. +1-1(2) = 1-2 = -1.
This means that calcium has a charge of +2 while nitrite ion has charge of -1, hence, when they combine, they exchange their charges, which become their subscript as follows:
Ca2+ + NO2- → Ca(NO2)2
Ca(NO2)2 is a stable ionic compound called calcium nitrite. Notice that it takes two atoms of NO2- to react with one atom of Ca2+.
