How much of a 24-gram sample of Radium-226 will remain unchanged at the end of three half-life periods?

Chemistry

1 answer:

shutvik [7]3 years ago

8 0

Answer:

The right answer is "3 g".

Explanation:

Given:

Initial mass substance,

$M_0=24 \ g$

By using the relation between half lives and amount of substances will be:

⇒ $M=\frac{M_0}{2^n}$

$=\frac{24}{2^3}$

$=3 \ g$

Thus, the above is the correct answer.

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Before it was launched, a helium-filled balloon had a pressure of 101 kPa at a temperature of 20°C. At an altitude of 15 000 m,

bogdanovich [222]

Answer:

5.54 m³.

Explanation:

We should use the ideal gas law: PV = nRT,

where, P is the pressure of the gas in atm,

V is the volume of the gas in L,

n is the number of moles in mole,

R is the general gas constant (R = 0.082 L.atm/mol),

T is the temperature of the gas in K.

We have two different cases at different (P, V and T) while the number of moles of He and R is constants.

∴ (P₁V₁) / (T₁) = (P₂V₂) / (T₂).

We can use P in KPa and V in m³ that the conversion factor can be canceled by division, but we should use T in K because its conversion factor is additive value.

P₁ = 101.0 kPa, V₁ = ??? m³, and T₁ = (20 °C + 273) = 293.0 K.

P₂ = 11.7 kPa, V₂ = 35.4 m³, and T₂ = (-56 °C + 273) = 217 K.

∴ The initial volume (V₁) = (P₂V₂T₁) / (P₁T₂) = (11.7 kPa)(35.4 m³)(293.0 K) / (101.0 kPa)(217.0 K) = (121354.74) / (21917) = 5.537 m³ ≅ 5.54 m³.

7 0

3 years ago

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miss Akunina [59]

Answer:

I can´t see, it isnt clear

Explanation:

8 0

3 years ago

1) Find the mass of 2.7 moles of NaCl.

sukhopar [10]

Answer: