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3 years ago

To 25mL of 0.90M HCl, 275mL do distilled water is added. What is the molarity of the resulting solution?

Chemistry

1 answer:

nalin [4]3 years ago

8 0

Answer:

0.075 M.

Explanation:

It is a dilution process.

We have the rule states that the no. of millimoles before dilution is equal to the no. of millimoles after dilution.

(MV) before dilution = (MV) after dilution

M before dilution = 0.90 M.

V before dilution = 25.0 mL.

M after dilution = ??? M.

V after dilution = V of HCl + V of water added = 25.0 mL + 275.0 mL = 300.0 mL.

∴ M after dilution = (MV) before dilution / V after dilution = (0.90 M)(25.0 mL) / (300.0 mL) = 0.075 M.

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What three (3) factors determine the reactivity of elements? Explain and give examples of each.

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Explanation:

The three factors which determine the reactivity of elements are as follows.

(1) Number of valence electrons.

(2) Size of an atom.

(3) Electro negativity of an atom.

All these factors are explained as follows.

(1) Number of valence electrons

According to the octet rule, every atom requires to attain stability. Therefore, number of electrons in the outermost shell will decide the reactivity of an atom as every atom needs to fill its shells or sub shells as per the octet rule. As a result, the reactivity increases.

For example, the atomic number of chlorine is 17 and its electronic configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}$

In the 3p sub shell, there is deficiency of one electron. So, in order to attain stability chlorine atom will react readily with another species or atom which can either donate or share one electron.

Whereas an atom with completely fill shell will have low reactivity.

(2) Size of an atom

On moving down the group size of atom increases. As a result, the attraction between the nucleus and electrons decreases due to the shielding effect. Thus, the larger is an atom, the more easily it can give electrons. Therefore, the reactivity increases.

For example, the atomic number of calcium is 20 and its electronic configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$

Also it is known that first shell of every atom can have 2 electrons, second shell can have 8 electrons, third shell can have 18 electrons and so on.

Since, calcium is larger in size as compared to beryllium and magnesium so it will readily loose 2 electrons to attain stability. Thus, it will attain a $Ca^{2+}$ charge.

(3) Electro negativity of an atom

An atom with uneven distribution of electrons will acquire a certain amount of charge. Thus, it becomes polar in nature and in order to gain stability, the atom will either loose or gain electrons according to its charge.

For example, atomic number of fluorine is 9 and its electronic configuration is $1s^{2}2s^{2}2p^{5}$ .

So, in order to gain stability fluorine will readily accept 1 electron to completely fill its 2p sub shell. As a result, the electronic configuration will become $1s^{2}2s^{2}2p^{6}$

Therefore, fluorine will have a charge of -1 because it has gained one electron.

3 0

3 years ago

What is the maximum volume of a 0.788 M CaCl2 solution that can be prepared using 85.3 g CaCl2?

Law Incorporation [45]

The answer is 0.975 L

Volume = mol/Molarity

We have molarity (0.788 M) and we need mol and volume. Let's first calculate number of moles of CaCl2 in 85.3 g:

Molar mass of CaCl2 is sum of atomic masses of Ca and Cl:
Mr(CaCl2) = Ar(Ca) + 2Ar(Cl) = 40 + 2 * 35.45 = 40 + 70.9 = 110.9 g/mol

So, if 110.9 g are in 1 mol, 85.3 g will be in x mol:
110.9 g : 1 mole = 85.3 g : x
x = 85.3 g * 1 mole / 110.9
x = 0.769 moles

Now, calculate the volume:
V = 0.769/0.788
V = 0.975 L

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3 years ago

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Rina8888 [55]

I believe that the chemical formula for an acid often begins with H, which means C is your answer.

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