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garri49 [273]
3 years ago
9

After decaying for 48 hours, l/16 of the original mass of a radioisotope sample remains unchanged. What is the half-life of this

radioisotope?
Chemistry
1 answer:
ivolga24 [154]3 years ago
3 0

After the first half-life, 1/2 is unchanged. After the 2nd one, 1/4 remains. After the 4th one, 1/16 remains. So you have 4 half-lives in 48 hours, the half-life is thus 12 hours.
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Five kilograms of liquid carbon tetrachloride undergo a mechanically reversible, isobaric change of state at 1 bar during which
Drupady [299]

Answer:

Explanation:

From the information given:

Mass of carbon tetrachloride = 5 kg

Pressure = 1 bar

The given density for carbon tetrachloride = 1590 kg/m³

The specific heat of carbon tetrachloride =  0.84 kJ/kg K

From the composition, the initial volume of carbon tetrachloride will be:= \dfrac{5 \ kg }{1590 \ kg/m^3}

= 0.0031 m³

Suppose \beta is independent of temperature while pressure is constant;

Then:

The change in volume can be expressed as:

\int ^{V_2}_{V_1} \dfrac{dV}{V} =\int ^{T_2}_{T_1} \beta dT

In ( \dfrac{V_2}{V_1})  = \beta (T_2-T_1)

V_2 = V_1 \times exp (\beta (T_2-T_1))

V_2 = 0.0031 \ m^3  \times exp  (1.2 \times 10^{-3} \times 20)

V_2 = 0.003175 \ m^3

However; the workdone = -PdV

W = -1.01 \times 10^5 \ Pa \times ( 0.003175 m^3 - 0.0031 \ m^3)

W = - 7.6 J

The heat energy Q = Δ h

Q = mC_p(T_2-T_1)

Q = 5 kg \times 0.84 \ kJ/kg^0 C \times 20

Q = 84 kJ

The internal energy is calculated by using the 1st law of thermodynamics; which can be expressed as;

ΔU = ΔQ + W

ΔU = 84 kJ + ( -7.6 × 10⁻³ kJ)

ΔU = 83.992 kJ

3 0
3 years ago
PLEASE HELP!!!! WILL GIVE BRANLIEST!!
NISA [10]

Answer:

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6 0
3 years ago
Read 2 more answers
How are the properties of thermosoftening and thermosetting polymers different? Use ​ideas about the structures of these two typ
stepan [7]

Thermosoftening plastics melt when they are heated.This means that they can be recycled , which involves melting them before making a new product. Thermosoftening plastics do not have covalent bonds between neighbouring polymer molecules, so the molecules can move over each other when heated and the plastic melts.

7 0
3 years ago
Calculate the energy E (in MeV) released in the following nuclear fission reaction: 242 Am + X → 90 Sr + 149 La + 4 n Start by c
KonstantinChe [14]

Answer:

177.993 MeV

Explanation:

Nuclear fission refers to a process where a nucleus is broken into smaller ones.

m(Am) = 242.0595490 u, m(Sr) = 89.9077387 u, m(La) = 148.934733 u and m(n) = 1.008665 u. To find the mass of X, we sum up the masses on both side and subtract them according to the equation given

242 + X = 90 +149 + 4

X = 243 - 242 = 1

so X is a neutron

next we calculate the Δm ( change in mass)

Δm = mass reactant - mass of product

(242.0595490 + 1.008665 ) - ( 89.9077387 + 148.934733  + 4 (1.008665))

= 243.068214 - 242.8771317 = 0.1910823 u

using the formula

E = (Δm) c² = 0.1910823 u × c² × \frac{931.5MeV}{c^2}× \frac{1}{u} = 177.993 MeV

8 0
4 years ago
Calculate the molarity of 8.42 x 102 mL of solution containing 22.4 g of potassium iodide.
givi [52]

Answer:

Molarity = 0.154 M

Explanation:

Given data:

Volume of solution = 8.42 × 10² mL ( 8.42 × 10² /1000 = 0.842 L)

Mass of potassium iodide = 22.4 g

Molarity of solution = ?

Solution:

Number of moles of potassium iodide:

Number of moles = mass/molar mass

Number of moles = 22.4 g/ 166.0 g/mol

Number of moles = 0.13 mol

Molarity:

Molarity = number of moles / volume in L

Molarity = 0.13 mol / 0.842 L

Molarity = 0.154 M

8 0
3 years ago
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