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antiseptic1488 [7]
3 years ago
11

What experimental observations indicate a chemical change is taking place?

Chemistry
1 answer:
Anestetic [448]3 years ago
6 0
A chemical change is characterized of the formation of new substances or a chemical reaction. There are a number of observations that we can see if this type of change happens. One would be the formation of gas bubbles, this indicates that one of the products is a gas. Another observation would be a formation of a precipitate in the solution, it would indicate that the new solid formed is not soluble in the solution. A permanent color change in the solution would also indicate a chemical change because it may be that the new substance that is formed has its own distinct color when in solution. 
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How many total atoms are in 0.670 g of p2o5?
scoray [572]

The molecular formula for compound is  P_{2}O_{5} mass of compound is 0.670 g.

To calculate number of atoms first calculate number of moles in the compound as follows:

n=\frac{m}{M}

Molar mass of  P_{2}O_{5} is 283.886 g/mol, thus,

n=\frac{0.670 g}{283.886 g/mol}=0.00236 mol

Thus, number of mole of P_{2}O_{5} is 0.00236 mol.

From the molecular formula 1 mole of P_{2}O_{5} has 2 mol of P (phosphorus) and 5 mol of O (oxygen).

Thus, number of moles of P and O in 0.00236 mol of P_{2}O_{5} will be:

n_{P}=2\times 0.00236 mol=0.00472 mol

Similarly,

n_{O}=5\times 0.00236 mol=0.0118 mol

Now, in 1 mol of an element there are 6.023\times 10^{23} atoms.

Number of atoms of P will be:

N_{P}=0.00472\times 6.023\times 10^{23}=2.84\times 10^{21}atoms

Similarly, number of atoms of O will be:

N_{O}=0.0118\times 6.023\times 10^{23}=7.11\times 10^{21}atoms

Total number of atoms will be sum of number of atoms of P and O:

N_{Total}=N_{P}+N_{O}=2.84\times 10^{21}+7.11\times 10^{21}=9.95\times 10^{21} atoms

Therefore, total number of atoms in P_{2}O_{5} will be 9.95\times 10^{21} atoms.

8 0
3 years ago
What does the atomic number of each atom represent?
saw5 [17]
It's the number of Protons of that atom..
6 0
3 years ago
What is the equilibrium constant, KC if the reaction is a gas phase reaction? (Ans.: Gas: KC = 0.328 dm3/mol)
valentina_108 [34]

Answer:

Equilibrium constant Kc = Qc = quotient of reactant(s) and product(s)

Kc = [C]x[D]y..../[A]m[B]n..... = 0.328dm3/mol, where [C]x[D]y is the product and [A]m[B]n is the reactant(Both in gaseous states)

Explanation:

When a mixture of reactants and products of a reaction reaches equilibrium at a given temperature, its reaction quotient always has the same value. This value is called the equilibrium constant (K) of the reaction at that temperature. As for the reaction quotient, when evaluated in terms of concentrations, it is noted as Kc.

That a reaction quotient always assumes the same value at equilibrium can be expressed as:

Qc (at equilibrium) = Kc =[C]x[D]y…/[A]m[B]n…

This equation is a mathematical statement of the law of mass action: When a reaction has attained equilibrium at a given temperature, the reaction quotient for the reaction always has the same value.

6 0
3 years ago
In an aqueous solution of a certain acid the acid is 4.4% dissociated and the pH is 3.03. Calculate the acid dissociation consta
NeX [460]

Answer:

4.1x10⁻⁵

Explanation:

The dissociation of an acid is a reversible reaction, and, because of that, it has an equilibrium constant, Ka. For a generic acid (HA), the dissociation happens by:

HA ⇄ H⁺ + A⁻

So, if x moles of the acid dissociates, x moles of H⁺ and x moles of A⁻ is formed. the percent of dissociation of the acid is:

% = (dissociated/total)*100%

4.4% = (x/[HA])*100%

But x = [A⁻], so:

[A⁻]/[HA] = 0.044

The pH of the acid can be calcualted by the Handersson-Halsebach equation:

pH = pKa + log[A⁻]/[HA]

3.03 = pKa + log 0.044

pKa = 3.03 - log 0.044

pKa = 4.39

pKa = -logKa

logKa = -pKa

Ka = 10^{-pKa}

Ka = 10^{-4.39}

Ka = 4.1x10⁻⁵

4 0
3 years ago
According to atomic theory:
JulsSmile [24]

Answer:

e. all of these

Explanation:

Let us check all the given options one by one:

a.The nucleus is positively charged.

Yes it is correct since nucleus contain protons and neutrons and protons are positively charged.

b.The nucleus contains both charged and uncharged particles.

Yes because protons are positively charged and neutrons are neutral in nature.

c.The electrons contribute very little to the total mass of the atom.

Yes we know all the mass of the atom is considered in center and mass of electron is negligible as compared to protons and neutrons.

d.The electrons are located in the atomic space outside the nucleus.

Yes, its a known fact.

e. All of these.

Since , all given options are correct .

Therefore , option e. is right .

7 0
3 years ago
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