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3 years ago

14. Carbon-14 emits beta radiation and decays with a half-life (t) of 5730 years. Assume

Chemistry

1 answer:

Marizza181 [45]3 years ago

6 0

Answer: 375 g

Explanation:

Formula used :

$a=\frac{a_o}{2^n}$

where,

a = amount of reactant left after n-half lives = ?

$a_o$ = Initial amount of the reactant = 100 g

n = number of half lives = 4

Putting values in above equation, we get:

$a=\frac{6000}{2^4}$

$a=375g$

Therefore, the amount of carbon-14 remains at the end of four half-lives is 375 g

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Find the pHpH of a solution prepared from 1.0 LL of a 0.15 MM solution of Ba(OH)2Ba(OH)2 and excess Zn(OH)2(s)Zn(OH)2(s). The Ks

charle [14.2K]

Answer:

pH = 13.09

Explanation:

Zn(OH)2 --> Zn+2 + 2OH- Ksp = 3X10^-15

Zn+2 + 4OH- --> Zn(OH)4-2 Kf = 2X10^15

K = Ksp X Kf

= 3*2*10^-15 * 10^15

= 6

Concentration of OH⁻ = 2[Ba(OH)₂] = 2 * 0.15 = 3 M

Zn(OH)₂ + 2OH⁻(aq) --> Zn(OH)₄²⁻(aq)

Initial: 0 0.3 0

Change: -2x +x

Equilibrium: 0.3 - 2x x

K = Zn(OH)₄²⁻/[OH⁻]²

6 = x/(0.3 - 2x)²

6 = x/(0.3 -2x)(0.3 -2x)

6(0.09 -1.2x + 4x²) = x

0.54 - 7.2x + 24x² = x

24x² - 8.2x + 0.54 = 0

Upon solving as quadratic equation, we obtain;

x = 0.089

Therefore,

Concentration of (OH⁻) = 0.3 - 2x

= 0.3 -(2*0.089)

= 0.122

pOH = -log[OH⁻]

= -log 0.122

= 0.91

pH = 14-0.91

= 13.09

4 0

3 years ago

Analysis of a gaseous chlorofluorocarbon, CClxFy, shows that it contains 11.79% C and 69.57% Cl. In another experiment, you find

uranmaximum [27]

Answer:

The molecular formula = $C_2Cl_{4}F_2$

Explanation:

$Moles =\frac {Given\ mass}{Molar\ mass}$

% of C = 11.79

Molar mass of C = 12.0107 g/mol

% moles of C = 11.79 / 12.0107 = 0.9816

% of Cl = 69.57

Molar mass of Cl = 35.453 g/mol

% moles of Cl = 69.57 / 35.453 = 1.9623

Given that the gaseous chlorofluorocarbon only contains chlorine, flourine and carbon. So,

% of F = 100% - % of C - % of C = 100 - 11.79 - 69.57 = 18.64

Molar mass of F = 18.998 g/mol

% moles of F = 18.64 / 18.998 = 0.9812

Taking the simplest ratio for C, Cl and F as:

0.9816 : 1.9623 : 0.9812

= 1 : 2 : 1

The empirical formula is = $CCl_2F$

Also, Given that:

Pressure = 21.3 mm Hg

Also, P (mm Hg) = P (atm) / 760

Pressure = 21.3 / 760 = 0.02803 atm

Temperature = 25 °C

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15

So,

T = (25 + 273.15) K = 298.15 K

Volume = 458 mL = 0.458 L (1 mL = 0.001 L)

Using ideal gas equation as:

PV=nRT

where,

P is the pressure

V is the volume

n is the number of moles

T is the temperature

R is Gas constant having value = 0.0821 L.atm/K.mol

Applying the equation as:

0.02803 atm × 0.458 L = n × 0.0821 L.atm/K.mol × 298.15 K

⇒n = 0.00052445 moles

Given that :

Amount = 0.107 g

Molar mass = ?

The formula for the calculation of moles is shown below:

$moles = \frac{Mass\ taken}{Molar\ mass}$

Thus,

$0.00052445= \frac{0.107\ g}{Molar\ mass}$

$Molar\ mass= 204.0233\ g/mol$

Molecular formulas is the actual number of atoms of each element in the compound while empirical formulas is the simplest or reduced ratio of the elements in the compound.

Thus,

Molecular mass = n × Empirical mass

Where, n is any positive number from 1, 2, 3...

Mass from the Empirical formula = 1×12.0107 + 2×35.453 + 1×18.998 = 101.9147 g/mol

Molar mass = 204.0233 g/mol

So,

Molecular mass = n × Empirical mass

204.0233 = n × 101.9147

⇒ n = 2

The molecular formula = $C_2Cl_{4}F_2$

6 0

4 years ago

Express In scientific notation. Remember, M must be a number 1 SM <10. 18 =

Nesterboy [21]

Answer: 1.8 x 10^1 or the scientific e notation is: 1.8e1

6 0

4 years ago

Read 2 more answers

. Guillermo was finding it difficult to walk up the steps to his family’s apartment. His doctor thinks that his cells might not

morpeh [17]

Answer:

Because oxygen is the combustion fuel and glucose is the substrate needed for synthesis of energy as ATPs during cellular respiration.Therefore Guillermo lacks enough energy as ATPs in her body cells, especially skeletal muscles cells to complete the task of ascending the s steps.

For all the mitochondrial in cells(sites of energy production) to receive needed glucose,and other metabolites needed for energy synthesis; an efficient transport system is needed, so that these materials are available immediately, in required amount. This system is called circulatory system.

And for the the supply of combustion fuel (oxygen) needed for the completion of the ATP synthesis mechanisms; respiratory systems which convey oxygen from the external environments to the circulatory system through breathing mechanisms, for distribution is needed.

Thus the doctor needs to test both the circulatory and respiratory systems.

Explanation:

4 0

3 years ago

A rectangular block has the following dimensions: 3.21 dm, 5.83 cm, and 1.84 in. The block has a mass of 1.94 kg. What is the de

spin [16.1K]

The density of the rectangular block in g/mL is 7.0.

Given the following data: