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3 years ago

Fill In The Blanks:

Chemistry

1 answer:

yawa3891 [41]3 years ago

5 0

Answers : Fill in the blanks.

Answer 1) During a chemical reaction, the sum of the masses of the reactants and products remain unchanged.

In a reaction masses of the reactants and products always remains the same.

Answer 2) In a pure chemical compound, elements are always present in a definite proportion by mass.

It is observed that in a chemical reaction the elements are found in definite proportion by mass.

Answer 3) Clusters of atoms that act as an ion are called polyatomic ions.

Polyatomic ions are those ions which consits of atoms more than two in their molecule.

Answer 4) In ionic compounds, the charge on each ion is used to determine the chemical formula of the compound.

The charges on the molecule helps to determine the chemical formula of any compound.

Answer 5) The Avogadro constant 6.022 X $10^{23}$ is defined as the number of atoms in exactly 12 g of carbon-12

Avogadro used carbon-12 as the standard reference element fpr determining its molecules.

Answer 6) Mass of 1 mole of a substance is called its molar mass or molecular weight.

A molecular weight of an atom to define its number of moles.

Answer 7) The abbreviation used for length names of elements are termed as their Symbols.

The abbreviation used for the length of names of elements are called as symbols.

Answer 8) A chemical formula is also known as a true formula or molecular formula.

The term chemical formula determines the number of chemical components present in it.

Answer 9) Those ions which are formed from single atoms are called monoatomic ions.

The ions made up from single atoms are called as monoatomic ions.

Answer 10) Ionic compounds are formed by the combination between metal and nonmetal.

The ionic compounds are usually bonded by the ionic bonds in a compound.

Answer 11) The valency of an ion is equal to the charge on the ion.

Valency of any ion is always equal to the charge on that ion.

Answer 12) Mole is a link between the mass of a substance and number of formula units.

Usually the mole forms a link to define the mass of the substance and its formula.

Answer 13) The SI unit of amount of a substance is mole.

Mole is considered to be the SI unit for aount of substance of any chemical compound.

Answer : true or false.

Answer 1) Formula mass of $Na_{2}$ O is 62 amu True

As we know there are 2 moles of Na and one mole of O so it will be (2 X 23) + 16 = 62 amu.

Answer 2) Those particles which have more or less electrons than the normal atoms are called ions True

We call ions to those atoms which hav more or less electrons in their normal atoms

Answer 3) Formula for sulphur dioxide is S $O_{3}$ . False

The formula for sulphur dioxide is S $O_{2}$ as the name di suggests two molecules.

Answer 4) Molar mass of ethyne (C2H2) is 26 g/mol True.

As the ethyene molecule consists of 2 C atoms and 2 H atoms it will be (12 X 2) + (2 X 1) = 26

Answer 5) 22 gm of CO2 consists of 1 mole. False

The 1 mole of C $O_{2}$ contains 1 C atom and 2 O atoms (12) + (16 X 2) = 44

Answer 6) Number of molecules in 32 gram of oxygen is 6.02 x $10^{23}$ . False

Only 1 moles of any substance will consist of 6.02 x $10^{23}$ molecules.

Answer 7) Water is an atom False.

Water is a molecule of 2 atoms namely hydrogen and oxygen.

Answer 8) Formula for sulphur dioxide is S $O_{2}$ true.

As the name suggest sulphur along with two oxygen in it.

Answer 9) Clusters of atoms that act as an ion is called polyatomic ion. True

The clusters of ions from different atoms of the elements can be called as polyatomic ions.

Answer 10) Mass of 1 mole of a substance is called its formula mass. False.

As in formula mass we take the sum of the atomic weights of atoms in a molecule. And for 1 mole of a substance it is called as molar mass.

Answer 11) In a pure chemical compound, elements are always present in a definite proportion by mass. True

In any chemical reaction, the pure chemical compound is always found to have elements with definite proportion to their masses.

You might be interested in

What is the difference between ionic and covalent bonding?

mr Goodwill [35]

In an ionic bond, one atom essentially donates an electron to stabilize the other atom. The atoms in an ionic bond have different electronegativity values from each other.

While in a covalent bond, the atoms are bound by shared electrons and the electronegativity values are the same.

8 0

3 years ago

Use the changes in oxidation numbers to identify which atom is oxidized, reduced, the oxidizing agent, and the reducing agent. 5

Vinil7 [7]

Answer:

Reaction A:

Hydrogen atoms in H₂ are oxidized.
Oxygen atoms in O₂ are reduced.
Hydrogen gas H₂ is the reducing agent.
Oxygen gas O₂ is the oxidizing agent.

Reaction B:

Oxygen atoms in KNO₃ are oxidized.
Nitrogen atoms in KNO₃ are reduced.
Potassium nitrate (V) KNO₃ is both the oxidizing agent and the reducing agent.

Explanation:

When an atom is oxidized, its oxidation number increases.
When an atom is reduced, its oxidation number decreases.
The oxidizing agent contains atoms that are reduced.
The reducing agent contains atoms that are oxidized.

Here are some common rules for assigning oxidation states.

Oxidation states on all atoms in a neutral compound shall add up to 0.
The average oxidation state on an atom is zero if the compound contains only atoms of that element. (E.g., the oxidation state on O in O₂ is zero.)
The oxidation state on oxygen atoms in compounds is typically -2. (Exceptions: oxygen bonded to fluorine, and peroxides.)
The oxidation state on group one metals (Li, Na, K) in compounds is typically +1.
The oxidation state on group two metals (Mg, Ca, Ba) in compounds is typically +2.
The oxidation state on H in compounds is typically +1. (Exceptions: metal hydrides where the oxidation state on H can be -1.)

For this question, only the rule about neutral compounds, oxygen, and group one metals (K in this case) are needed.

<h3>Reaction B</h3>

Oxidation states in KNO₃:

K is a group one metal. The oxidation state on K in the compound KNO₃ shall be +1.
The oxidation state on N tend to vary a lot, from -3 all the way to +5. Leave that as $x$ for now.
There's no fluorine in KNO₃. The ion NO₃⁻ stands for nitrate. There's no peroxide in that ion. The oxidation state on O in this compound shall be -2.
Let the oxidation state on N be $x$ . The oxidation state of all five atoms in the formula KNO₃ shall add up to zero. $1\times (+1) + 1 \times (x) + {\bf 3} \times (-2) = 0\\x = +5$ . As a result, the oxidation state on N in KNO₃ will be +5.

Similarly, for KNO₂:

The oxidation state on the group one metal K in KNO₂ will still be +1.
Let the oxidation state on N be $y$ .
There's no peroxide in the nitrite ion, NO₂⁻, either. The oxidation state on O in KNO₂ will still be -2.
The oxidation state on all atoms in this formula shall add up to 0. Solve for the oxidation state on N: $1\times (+1) + 1 \times (y) + {\bf 2}\times (-2) = 0\\y = +3$ . The oxidation state on N in KNO₂ will be +3.

Oxygen is the only element in O₂. As a result,

The oxidation state on O in O₂ will be 0.

$\rm\stackrel{+1}{K}\stackrel{\bf +5}{N}\stackrel{\bf -2}{O}_3 \to \stackrel{+1}{K}\stackrel{\bf+3}{N}\stackrel{\bf -2}{O}_2 + \stackrel{\bf 0}{O}_2$ .

The oxidation state on two oxygen atoms in KNO₃ increases from -2 to 0. These oxygen atoms are oxidized. KNO₃ is also the reducing agent.

The oxidation state on the nitrogen atom in KNO₃ decreases from +5 to +3. That nitrogen atom is reduced. As a result, KNO₃ is also the oxidizing agent.

<h3>Reaction A</h3>

Apply these steps to reaction A.

H₂:

Oxidation state on H: 0.

O₂:

Oxidation state on O: 0.

H₂O:

Oxidation state on H: +1.
Oxidation state on O: -2.
Double check: ${\bf 2} \times (+1) + (-2) = 0$ .

$\rm \stackrel{}{2}\; \stackrel{\bf 0}{H}_2 + \stackrel{\bf 0}{O}_2\stackrel{}{\to} \stackrel{}{2}\;\stackrel{\bf +1}{H}_2\stackrel{\bf -2}{O}$ .

The oxidation state on oxygen atoms decreases from 0 to -2. Those oxygen atoms are reduced. O₂ is thus the oxidizing agent.

The oxidation state on hydrogen atoms increases from 0 to +1. Those hydrogen atoms are oxidized. H₂ is thus the reducing agent.

4 0

3 years ago

According to Dalton, if 2 grams of element X combine with 4 grams of element Y to form compound XY, how many grams of element X

adell [148]

The ratio of reactant in grams would be influenced by the reaction equation and the molar mass of the elements. But the ratio of a reactant needed in grams would be same for a reaction.
If 2 grams of element X combine with 4 grams of element Y to form compound XY, it means the ratio of reactant in grams<span> would be 2:4 or 1:2

The number of element X needed for 28grams of element Y would be:
1/2 * 28grams = 14 grams.</span>

8 0

3 years ago

What is the concentration (in M) of a 225ml potassium sulfate solution that contains 4.15g of potassium?

mars1129 [50]

The concentration of solution in M or mol/L can be calculated using the following formula:

$C=\frac{n}{V}$ .... (1)

Here, n is number of moles and V is volume of solution in L.

The molecular formula of potassium sulfate is $K_{2}SO_{4}$ thus, there are 2 moles of potassium in 1 mol of potassium sulfate.

1 mol of potassium will be there in 0.5 mol of potassium sulfate.

Mass of potassium is 4.15 g, molar mass is 39.1 g/mol.

Number of moles can be calculated as follows:

$n=\frac{m}{M}$

Here, m is mass and M is molar mass

Putting the values,

$n=\frac{(4.15 g}{(39.1 g/mol}=0.1061 mol$

Thus, number of moles of $K_{2}SO_{4}$ will be $0.1061\times 0.5=0.053 mol$ .

The volume of solution is 225 mL, converting this into L,

$1 mL=10^{-3}L$

Thus,

$225 mL=0.225 L$

Putting the values in equation (1),

$C=\frac{(0.053 mol}{0.225 L}=0.236 M$

Therefore, concentration of potassium sulfate solution is 0.236 M.

4 0

3 years ago

Under standard-state conditions, which of the following species is the best reducing agent? a. Ag+ b. Pb c. H2 d. Ag e. Mg2+

eimsori [14]

<u>Answer:</u> The correct answer is Option b.

<u>Explanation:</u>

Reducing agents are defined as the agents which help the other substance to get reduced and itself gets oxidized. They undergo oxidation reaction.

$X\rightarrow X^{n+}+ne^-$

For determination of reducing agents, we will look at the oxidation potentials of the substance. Oxidation potentials can be determined by reversing the standard reduction potentials.

For the given options:

<u>Option a:</u> $Ag^+$

This ion cannot be further oxidized because +1 is the most stable oxidation state of silver.

<u>Option b:</u> $Pb$

This metal can easily get oxidized to $Pb^{2+}$ ion and the standard oxidation potential for this is 0.13 V

$Pb\rightarrow Pb^{2+}+2e^-;E^o_{(Pb/Pb^{2+})}=+0.13V$

<u>Option c:</u> $H_2$

This metal can easily get oxidized to $H^{+}$ ion and the standard oxidation potential for this is 0.0 V

$H_2\rightarrow 2H^++2e^-;E^o_{(H_2/H^{+})}=0.0V$

<u>Option d:</u> $Ag$

This metal can easily get oxidized to $Ag^{+}$ ion and the standard oxidation potential for this is -0.80 V

$Ag\rightarrow Ag^{+}+e^-;E^o_{(Ag/Ag^{+})}=-0.80V$

<u>Option e:</u> $Mg^{2+}$

This ion cannot be further oxidized because +2 is the most stable oxidation state of magnesium.

By looking at the standard oxidation potential of the substances, the substance having highest positive $E^o$ potential will always get oxidized and will undergo oxidation reaction. Thus, considered as strong reducing agent.

From the above values, the correct answer is Option b.

8 0

3 years ago