If a 3.0 picogram (pg) sample of curium-245 has a half-life of 8500 years, which conclusion can be drawn?

How do you know if an atom is stable?

MArishka [77]

Talk to it about it's emotions and if it breaks down crying immediately then it is unstable.

4 0

3 years ago

Calculate the concentrations of all species present in a 0.26 M solution of ethylammonium chloride (C2H5NH3Cl).

Alina [70]

Answer:

0.00000223

Explanation:

pKa for C2H5NH3+ = 10.7

pKw = 14.0

pKa + pKb = pKw

10.7 + pKb = 14.0

pKb = 14.0 - 10.7

pKb = 3.30

C2H5NH3Cl is a salt of ethylamine and HCl so it will dissolve in water to produce C2H5NH3^+ + Cl^-

The base hydrolysis reaction: C2H5NH3^+(aq) + H2O(l) <=> C2H5NH2(aq) + H3O^+(aq)

This reaction is described by Kb.

Kb = [C2H5NH2][H3O^+]/[C2H5NH3^+]

Let [C2H5NH2] = [H3O^+] = x,

so [C2H5NH3^+] = 0.26 - x

Kb = x^2/(0.26 - x) = 2.00 x 10^-11

Let's solve for x. In this equation, It is possible to solve without the use quadratic equation. So we can assume that 0.26 - x is approximately equal to 0.26. We won't know until we do the calculation.

We get: x^2 + 2.00 x 10^-11x - 4.99 x 10^-12 = 0

With the use of a quadratic calculator.

x = 2.23 x 10^-6 M = [C2H5NH2] = [H3O^+]

0.26 - x is just 0.26 M in this problem because 2.23 x 10^-6 M is insignificant.

[C2H5NH3^+] = 0.26 M = [Cl^-]

NOTE:

pH = -log [H3O^+] = -log(2.23 x 10^-6) = 5.65

Ka is the acid dissociation constant

Kb is the base dissociation constant

5 0

3 years ago

What volume of oxygen at STP is requieres for the complete combustion of 100.50 mL of C2H2

malfutka [58]

The volume of oxygen at STP required would be 252.0 mL.

<h3>Stoichiometic problem</h3>

The equation for the complete combustion of C2H2 is as below:

$2C_2H_2 + 5O_2 --- > 4CO_2 + 2H_2O$

The mole ratio of C2H2 to O2 is 2:5.

1 mole of a gas at STP is 22.4 L.

At STP, 100.50 mL of C2H2 will be:

100.50 x 1/22400 = 0.0045 mole

Equivalent mole of O2 according to the balanced equation = 5/2 x 0.0045 = 0.01125 moles

0.01125 moles of O2 at STP = 0.01125 x 22400 = 252.0 mL

Thus, 252.0 mL of O2 gas will be required at STP.

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7 0

1 year ago

in a mixture of 1.90 mol of gas, 0.85 mol are nitrogen (n2) molecules. what is the mole fraction of n2 in this mixture?

Nostrana [21]

0.447 is the mole fraction of Nitrogen in this mixture.

mole fraction of nitrogen= moles of nitrogen/total moles

mole fraction of nitrogen=0.85/1.90

mole fraction of nitrogen=0.447

The product of the moles of a component and the total moles of the solution yields a mole fraction, which is a unit of concentration measurement. Because it is a ratio, mole fraction is a unitless statement. The sum of the components of the mole fraction of a solution is one. In a mixture of 1 mol benzene, 2 mol carbon tetrachloride, and 7 mol acetone, the mole fraction of the acetone is 0.7. This is computed by dividing the sum of the moles of acetone in the solution by the total number of moles of the solution's constituents:

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4 0

9 months ago

A gas has experienced a small increase in volume but has maintained the same pressure and number of moles. According to the idea

krek1111 [17]

Answer:

If a gas has experienced a small increase in volume but has maintained the same pressure and number of moles, the temperature of the gas will DROP.

Explanation:

According to Boyle’s law of ideal gases, volume and temperature of a gas is inversely related, as long as the pressure is kept constant;

P₁V₁/T₁ = P₂V₂/T₂

Therefore, if the volume of the gas increases, the temperature will definitely decrease due to the inverse relationship. The gas will get cooler.