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skad [1K]
4 years ago
11

The half-life of bismuth-210, 210bi, is 5 days. (a) if a sample has a mass of 184 mg, find the amount remaining after 15 days.

Chemistry
1 answer:
ASHA 777 [7]4 years ago
3 0

Answer:- 23.0 mg

Solution:- Radioactive decay obeys first order kinetics and the first order kinetics equation is:

lnN=-kt+lnN_0

where, N_0 is the initial amount of radioactive substance and N is it's amount after time t. k is the decay constant.

From given information, Original amount, N_0 of the radioactive substance is 184 mg and we are asked to calculate the amount N after 15 days. It means, t = 15 days

Half life is given as 5 days. From the half life, we could calculate the decay constant k using the equation:

k=\frac{0.693}{t_1_/_2}

where, t_1_/_2 is the symbol for half life. let's plug in the value of half like to calculate k:

k=\frac{0.693}{5days}

k=0.1386day^-^1

Let's plug in the values in the first order kinetics equation and solve it for N:

lnN=-0.1386day^-^1(15days)+ln184mg

lnN=-2.079+5.215

lnN = 3.136

N=e^3^.^1^3^6

N = 23.0 mg

So, 23.0 mg of Bi-210 would be remaining after 15 days.

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Explanation: ΔG is the representation of the change in Gibbs Free Energy and relates enthalpy and entropy in a single value, which is:

ΔG = ΔH - TΔS

where:

ΔH is enthalpy

T is temperature

ΔS is entropy (measure of the )

It can also predict the direction of the reaction with the conditions of temperature and pressure being constant.

When the change is positive, the reaction is non-spontaneous, which means the reaction needs external energy to occur. If the change is negative, it is spontaneous, i.e., happens without external help.

Analyzing the reaction, we see that reaction A and B have a positive ΔG, while reaction C is negative, so the reaction that are unfavorable or nonspontaneous are <u>reactions A and B</u>.

6 0
3 years ago
2. What is the approximate mass of an atom that
ratelena [41]

Answer:

b. 45 u

Explanation:

the mass of an atom is equal to the protons plus neutrons:

26+19=45

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3 0
3 years ago
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4. Aluminum Sulfate + Magnesium Chloride à Aluminum<br> chloride + Magnesium Sulfate
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Gold has a molar (atomic) mass of 197 g/mol. consider a 2.47 g sample of pure gold vapor. (a) calculate the number of moles of g
adell [148]
N = given mass/ molar mass.
n = number of moles
given mass = 2.47 g
molar mass = 197 g/mol

n = 2.47 / 197 
n = 0.01253 moles.
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3 0
4 years ago
A sample of liquid heptane (C7H16) weighing 11.5 g is reacted with 1.3 mol of oxygen gas. The heptane is burned completely (hept
Anna11 [10]

Answer:

a) 0.525 mol

b) 0.525 mol

c) 0.236 mol

Explanation:

The combustion reactions (partial and total) will be:

C₇H₁₆ + (15/2)O₂ → 7CO + 8H₂O

C₇H₁₆ + 11O₂ → 7CO₂ + 8H₂O

---------------------------------------------------

2C₇H₁₆ + (37/2)O₂ → 7CO + 7CO₂ + 16H₂O

It means that the reaction will form 50% of each gas.

a) 0.525 mol of CO

b) 0.525 mol of CO₂

c) The molar mass of heptane is: 7*12 g/mol of C + 16*1 g/mol of H = 100 g/mol

So, the number of moles is the mass divided by the molar mass:

n = 11.5/100 = 0.115 mol

For the stoichiometry:

2 mol of C₇H₁₆ -------------- (37/2) mol of O₂

0.115 mol of C₇H₁₆ --------- x

By a simple direct three rule:

2x = 2.1275

x = 1.064 mol of O₂

Which is the moles of oxygen that reacts, so are leftover:

1.3 - 1.064 = 0.236 mol of O₂

5 0
4 years ago
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