Tag: atoms, molecules and radicals

Questions Related to atoms, molecules and radicals

A formula tells about :

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. number of atoms present in one molecule

  2. gives mathematical formula

  3. an element

  4. the source of the compound

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Correct Option: A
Explanation:

Molecular formulas describe the exact number and type of atoms in a single molecule of a compound. The constituent elements are represented by their chemical symbols, and the number of atoms of each element present in each molecule is shown as a subscript following that element's symbol. The molecular formula expresses information about the proportions of atoms that constitute a particular chemical compound, using a single line of chemical element symbols and numbers. Sometimes it also includes other symbols, such as parentheses, dashes, brackets, and plus (+) and minus (–) signs.

The molecular formula is a short form representation of

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. A compound

  2. An element

  3. A mixture

  4. An alloy

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Correct Option: A
Explanation:

 A chemical formula that shows the total number and kinds of atoms in a molecule, but not their structural arrangement or the molecular formula is a short form representation of a compound.

When naming a binary compound, what determines the prefix for an element in a compound?

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. The number of atoms of that element in the compound

  2. The number of valence electrons in the element

  3. The total number of atoms in the compound

  4. The number of shared electrons in the compound

  5. The number of different elements in the compound

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Correct Option: A
Explanation:

When naming a binary compound, the number of atoms of that element in the compound determines the prefix for an element in a compound.
For example, while naming  $N _2O _3 $, the prefix di is used for $N$ which indicates $2 N$ atoms and the prefix tri is used for $O$ which indicates $3 O$ atoms. Hence, the name dintirogen trioxide.

The salt of an oxyacid of a metal M contains one sulphur and four oxygen atoms

The oxyacid of the salt is

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. $H _{2}SO _{4}$

  2. $H _{2}SO _{3}$

  3. $H _{2}S _{2}O _{7}$

  4. $H _{2}S$

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Correct Option: A
Explanation:

The salt of an oxyacid of a metal M contains one sulphur and four oxygen atoms. The oxyacid of the salt is $H _{2}SO _{4}$. One sulphur and four oxygen atoms indicate sulphate ion $(SO _4^{2-})$. Hence, the salt is metal sulphate and the oxyacid is sulphuric acid.

The trivial name of $Na _{2}CO _{3}$ is:

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. soda ash

  2. soda carb

  3. soda

  4. baking soda

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Correct Option: A
Explanation:

Trivial name of $Na _2CO _3\longrightarrow$ Soda Ash

Chemical name of $Na _2CO _3\longrightarrow$ Sodium Carbonate
A chemical formula is of great importance
$\longrightarrow$ Name of compounds are represented by the chemical formula.
Example: Sodium bicarbonate$\longrightarrow NaHCO _3$
Sulphuric acid $\longrightarrow H _2SO _4$
$\longrightarrow$ It is known by chemical formula how many atoms of a particular element are present in the compound.
Example: Phosphoric acid
$H _3PO _4$ shows that there are $3$ atoms of hydrogen, $1$ atom of Phosphorus and $4$ atoms of oxygen.
$\longrightarrow$ It represents what elements are present in the compound by its symbol.
Example:- $NaCl\longrightarrow$ Sodium chloride has sodium and chlorine in it.

The general formula of one molecule of a metallic halide can be

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. MX

  2. $MX _{2}$

  3. $MX _{3}$

  4. $M _{2}X$

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Correct Option: A,B,C
Explanation:

The general formula of one molecule of a metallic halide can be-

$MX = NaCl$
$MX _2 =MgCl _2$
$MX _3 = AlCl _3$
All halogens are monovalent hens $M _2X$ is not possible.

The chemical formula of the compound containing carbon and chlorine is:

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. $CCl _2$

  2. $CCl _3$

  3. $CCl _4$

  4. $C _2Cl _4$

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Correct Option: C
Explanation:

Carbon has a valency of$ +4$ and chlorine has a valency equal to $-1. $Compound is Carbon tetrachloride $CCl _4$.

Predict the formulae of the binary compounds formed by combination of the following pairs of elements:
(i)    Magnesium and nitrogen
(ii)   Silicon and oxygen

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. $MgN _{2}, SiO _{2}$

  2. $Mg _{3}N _{2}, SiO _{2}$

  3. $Mg _{2}N _{3}, Si _{2}O _{3}$

  4. $MgN, SiO _{2}$

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Correct Option: B
Explanation:

Three Mg ( $+2$ oxidation state) combine with two N ($-3$ oxidation state) to form $Mg _3N _2$.

One Si ( $+4$ oxidation state) combine with two O ($-2$ oxidation state) to form $SiO _2$.

Note: In a neutral molecule, the total charge on cations is numerically equal to the total charge on anions.

Predict the formula of stable compound formed by an element with atomic number 114 and fluorine.

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. $AF _{3}$

  2. $AF _{2}$

  3. $AF$

  4. $AF _{4}$

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Correct Option: D
Explanation:
Element A with atomic number 114 will share four electrons to attain stable noble gas electronic configuration. It falls in the Carbon family.

Fluorine shares one electron to attain stable noble gas electronic configuration. One atom of A combines with four atoms of F to form $AF _4$.

Hence, the correct option is $\text{D}$

A gas is heated through 1°C in a closed vessel and so the pressure increases by 0.4%. The initial temperature of the gas was

chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

  1. $-23^0C$

  2. $23^0C$

  3. $250^0C$

  4. $523^0C$

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Correct Option: A
Explanation: