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3 years ago

How many neutrons does element X have if its atomic number is 31 and its mass number is 80?

Chemistry

1 answer:

MrRissso [65]3 years ago

5 0

49 neutrons in each nucleus.

<h3>Explanation</h3>

For each nucleus:

Mass number = Number of protons + Number of neutrons.

The atomic number of a nucleus is the same as its number of protons. The atomic number of the nucleus here is 31. There are 31 protons in each nucleus.

Mass number = 80;
Number of protons = Atomic number = 31;
The number of neutrons is to be found.

Again,

Mass number = Number of protons + Number of neutrons.

80 = 31 + Number of neutrons.

Number of neutrons = 80 - 31 = 49.

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Calculate the freezing point of a solution containing 5.0 grams of KCl and 550.0 grams of water. The molal-freezing-point-depres

yulyashka [42]

<u>Answer:</u> The freezing point of solution is -0.454°C

<u>Explanation:</u>

Depression in freezing point is defined as the difference in the freezing point of pure solution and freezing point of solution.

The equation used to calculate depression in freezing point follows:

$\Delta T_f=\text{Freezing point of pure solution}-\text{Freezing point of solution}$

To calculate the depression in freezing point, we use the equation:

$\Delta T_f=iK_fm$

Or,

$\text{Freezing point of pure solution}-\text{Freezing point of solution}=i\times K_f\times \frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ (in grams)}}$

where,

Freezing point of pure solution = 0°C

i = Vant hoff factor = 2

$K_f$ = molal freezing point elevation constant = 1.86°C/m

$m_{solute}$ = Given mass of solute (KCl) = 5.0 g

$M_{solute}$ = Molar mass of solute (KCl) = 74.55 g/mol

$W_{solvent}$ = Mass of solvent (water) = 550.0 g

Putting values in above equation, we get:

$0-\text{Freezing point of solution}=2\times 1.86^oC/m\times \frac{5\times 1000}{74.55g/mol\times 550}\\\\\text{Freezing point of solution}=-0.454^oC$

Hence, the freezing point of solution is -0.454°C

3 0

3 years ago

How many moles of Co2 are produced when 0.2 moles of sodium carbonate reacts with excess HCl

Pie

To determine the number of moles of carbon dioxide that is produced, we need to know the reaction of the process. For the reaction of HCl and sodium carbonate, the balanced chemical equation would be expressed as:

2HCl + Na2CO3 = 2NaCl + H2O + CO2

From the initial amount given of sodium carbonate and the relation of the substances from the balanced reaction, we calculate the moles of carbon dioxide as follows:

0.2 moles Na2Co3 ( 1 mol CO2 / 1 mol Na2Co3 ) = 0.2 moles CO2

Therefore, the amount in moles of carbon dioxide that is produced from 0.2 moles sodium carbonate would be 0.2 moles as well.

5 0

3 years ago

How many atoms of S are in the following formula: 3Na(SO4)2<br><br> 1) 6<br> 2) 8<br> 3) 3<br> 4) 5

larisa [96]

Answer:

Explanation:

7 0

2 years ago

What process is used to refine aluminum from its ore bauxite?

Murljashka [212]

Answer:

D. Smelting

Explanation:

Bauxite is the aluminum ore from which alumina, also known as aluminum oxide, Al₂O₃, is produced. Bauxite is extracted from the topsoil regions of some subtropical and tropical regions, and the Bayer process is primarily then used to produce alumina from the bauxite.

Aluminum is produced from the alumina by an aluminum smelting process known as the Hall—Heroult electrolytic process which involves the use of a carbon anode and direct current to produce aluminum by reducing the aluminum oxide

7 0

3 years ago

What is the concentration in molarity of S2O32- (aq) in a solution prepared by mixing 150 mLmL of 0.149 MM Na2S2O3 (aq) with eno

Artist 52 [7]

Answer:

0.0890 M

Explanation:

Since the concentration of KCl is irrelevant in this case, the concentration of Na2S2O3 can be determined using a simple dilution equation:

C1V1 = C2V2, where C1 = 0.149 M, V1 = 150 mL, V2 = 250 mL

C2 = 0.149 x 150/250

= 0.089 M

To determine the concentration of S2O32- (aq), consider the equation:

$Na_2S_2O_3 => 2Na^+_{(aq)} + S_2O^2^-_3_{(aq)}$

The concentration of Na2S2O3 and S2O32- (aq) is 1:1

Hence, the concentration in molarity of S2O32- (aq) is 0.089 M.

To 3 significant figures = 0.0890 M

7 0

3 years ago