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Lerok [7]
3 years ago
11

How many atoms of beryllium are equal to 0.39 moles of beryllium?

Chemistry
1 answer:
FinnZ [79.3K]3 years ago
3 0

Answer:

2.35 x 10²³atoms

Explanation:

Given parameters:

Number of moles of Be  = 0.39moles

Unknown:

Number of atoms  = ?

Solution:

To solve this problem:

                1 mole of a substance contains 6.02 x 10²³ atoms

               0.39 mole of Be will contain 0.39 x 6.02 x 10²³ = 2.35 x 10²³atoms

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When 136g of glycine are dissolved in of a certain mystery liquid , the freezing point of the solution is lower than the freezin
loris [4]

The given question is incomplete. The complete question is:

When 136 g of glycine are dissolved in 950 g of a certain mystery liquid X, the freezing point of the solution is 8.2C lower than the freezing point of pure X. On the other hand, when 136 g of sodium chloride are dissolved in the same mass of X, the freezing point of the solution is 20.0C lower than the freezing point of pure X. Calculate the van't Hoff factor for sodium chloride in X.

Answer: The vant hoff factor for sodium chloride in X is 1.9

Explanation:

Depression in freezing point is given by:

\Delta T_f=i\times K_f\times m

\Delta T_f=T_f^0-T_f=8.2^0C = Depression in freezing point

K_f = freezing point constant

i = vant hoff factor = 1 ( for non electrolyte)

m= molality =\frac{136g\times 1000}{950g\times 75.07g/mol}=1.9

8.2^0C=1\times K_f\times 1.9

K_f=4.32^0C/m

Now Depression in freezing point for sodium chloride is given by:

\Delta T_f=i\times K_f\times m

\Delta T_f=20.0^0C = Depression in freezing point

K_f = freezing point constant  

m= molality = \frac{136g\times 1000}{950g\times 58.5g/mol}=2.45

20.0^0C=i\times 4.32^0C\times 2.45

i=1.9

Thus vant hoff factor for sodium chloride in X is 1.9

3 0
3 years ago
What is force and motion
Elza [17]
Force is a strength or energy as an attribute or physical action or movement, motion is the action or process of moving or being moved
5 0
3 years ago
Read 2 more answers
A student heats 2.796g of zinc powder with 2.414g of sulphur.He reported that he obtained 4.169g of zinc sulfide and recover 1.0
Sati [7]

Answer:

The mass of reactants and products are equal hence the reaction obeys law of conservation of mass

Explanation:

The law of mass conservation states that for a closed system to all transfer of mass, the mass of system must remain constant over time. This means for a chemical reaction, the mass of reactants must equal the mass of products.

if 2.796g of Zn reacts with 2.414g of sulphur to produce 4.169g of ZnS ad 1.041g of unreacted sulphur, then it means that accorfing to the law of mass conservation, the mass of reactants (zinc and sulphur), must be equal to mass of products (zinc sulfide and unreacted sulphur)

Mass of reactants = 2.796g + 2.414g =5.21g

Mass of products = 4.169g + 1.041g=5.21g

5 0
3 years ago
Calculate the standard enthalpy change for the reaction at 25 ∘ 25 ∘ C. Standard enthalpy of formation values can be found in th
WINSTONCH [101]

<u>Answer:</u> The standard enthalpy change of the reaction is coming out to be -16.3 kJ

<u>Explanation:</u>

Enthalpy change is defined as the difference in enthalpies of all the product and the reactants each multiplied with their respective number of moles. It is represented as \Delta H

The equation used to calculate enthalpy change is of a reaction is:  

\Delta H_{rxn}=\sum [n\times \Delta H_f(product)]-\sum [n\times \Delta H_f(reactant)]

For the given chemical reaction:

Mg(OH)_2(s)+2HCl(g)\rightarrow MgCl_2(s)+2H_2O(g)

The equation for the enthalpy change of the above reaction is:

\Delta H_{rxn}=[(1\times \Delta H_f_{(MgCl_2(s))})+(2\times \Delta H_f_{(H_2O(g))})]-[(1\times \Delta H_f_{(Mg(OH)_2(s))})+(2\times \Delta H_f_{(HCl(g))})]

We are given:

\Delta H_f_{(Mg(OH)_2(s))}=-924.5kJ/mol\\\Delta H_f_{(HCl(g))}=-92.30kJ/mol\\\Delta H_f_{(MgCl_2(s))}=-641.8kJ/mol\\\Delta H_f_{(H_2O(g))}=-241.8kJ/mol

Putting values in above equation, we get:

\Delta H_{rxn}=[(1\times (-641.8))+(2\times (-241.8))]-[(1\times (-924.5))+(2\times (-92.30))]\\\\\Delta H_{rxn}=-16.3kJ

Hence, the standard enthalpy change of the reaction is coming out to be -16.3 kJ

6 0
3 years ago
If I have 17 liters of gas at 67C and 88.89 atm, what will be the pressure of the gas if I raise the temperature to 94C and decr
dmitriy555 [2]

Answer:

The correct answer is A. 140 atm

Explanation:

We use the gas formula, which results from the combination of the Boyle, Charles and Gay-Lussac laws. According to which at a constant mass, temperature, pressure and volume vary, keeping constant PV / T. We convert the unit Celsius into Kelvin:

0 ° C = 273K, 67 ° C = 273 + 67 = 340K; 94 ° C = 273 + 94 = 367K

P1xV1 /T1= P2x V2/T2

P2= ((P1xV1 /T1)xT2)/V2

P2=((88,89atm x 17L/340K)x367K)/12L= <em>135,927625 atm</em>

7 0
3 years ago
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