Answer;
(3) Substance A is an element and substance Z is a compound.
Explanation;
-A compound is a substance formed when two or more chemical elements are chemically bonded together, such as water, carbon dioxide, methane, etc while an element is a pure chemical substance made of same type of atoms, such includes, oxygen, potassium, hydrogen, carbon, etc.
- Compounds can be brokendown or decomposed into simpler substances: elements cannot be broken down chemically into simpler substances .
Answer: Option (d) is the correct answer.
Explanation:
It is known that sea water contains a large amount of common salt, that is, sodium chloride (NaCl). This salt is basic in nature.
Since, it is also known that species which have pH equals to 7 are basic in nature. Species which have pH less than 7 are acidic in nature and species which have pH greater than 7 are basic in nature.
Hence, due to the presence of common salt in sea water its surface is basic in nature.
Therefore, we can conclude that the normal pH of surface sea water is 9.0.
b. a covalent compound because it has a low boiling point
c.an ionic compound because it has a low melting point
d.a covalent compound because it has a low melting point
Answer: A solid compound in a sealed container is a covalent compound because it has a low melting point.
Explanation:
Ionic compounds have strong electrostatic forces which are strong in nature and cannot be broken down at low temperature.
Whereas covalent compounds have Vanderwaal forces which are weak in nature. Therefore, covalent compounds melts at low temperature.
Thus, it can be concluded that a solid compound in a sealed container is a covalent compound because it has a low melting point.
Answer: The answer is d
Explanation:
B) The smallest unit of P4.
C) The smallest unit of NH3.
D) The smallest unit of H2O.
Answer:
Option A
Explanation:
An atom is the smallest particle of a chemical element that can exist.
Using the method of elimination;
Option A - This correct because an atom is the smallest unit of a chemical element ( Neon). It fits the definition given above.
Option B - This option is wrong because P4 is a substance that is made up of four atoms of the same element, so it is a molecular element and not an atom.
A chemical compound is a chemical substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds.
Option C - This option is wrong because NH3 is a compound containing two different elements.
Option D - This option is wrong because H2O is a compound containing two different elements.
Rubidium (Rb)
Ionization Energy is defined as, "the minimum energy required to knock out or remove the valence electron from valence shell of an atom".
Along Periods:
Ionization Energy increases from left to right along the periods because moving from left to right in the same period the number of protons (atomic number) increases but the number of shells remain constant hence, resulting in strong nuclear interactions and electrons are more attracted to nucleus hence, requires more energy to knock them out.
Along Groups:
Ionization energy decreases from top to bottom along the groups because the number of shells increases and the distance between nucleus and valence electrons also increases along with increase in shielding effect provided by core electrons. Therefore, the valence electrons experience less nuclear attraction and are easily removed.
Given elements belong to same group hence, Rubidium present at the bottom of remaining elements will have least ionization energy due to facts explained in trends of groups above.
(2) Ca (4) Na
Carbon dioxide, ethanol, and energy
Lactic acid and energy
Glucose, oxygen, and energy