A sample contains 10.5 g of the radioisotope Pb-212 and 157.5 g of its daughter isotope, Bi-212. How many half-lives have passed since the sample originally formed?4
14
15
147.5
Answers
Answer: The sample must have passed 4 half-lives after the sample was originally formed.
Explanation: This is a type of radioactive decay and all the radioactive process follow first order kinetics.
Equation for the reaction of decay of radioisotope follows:
To calculate the initial amount of , we will require the stoichiometry of the reaction and the moles of the reactant and product.
Expression for calculating the moles is given by:
Moles of left =
Moles of
By the stoichiometry of above reaction,
1 mole of is produced by 1 mole
So, 0.7429 moles of will be produced by =
Amount of decomposed will be = 0.7429 moles
Initial amount of will be = Amount decomposed + Amount left = (0.0495 + 0.7429)moles = 0.7924 moles
Now, to calculate the number of half lives, we use the formula:
where,
a = amount of reactant left after n-half lives = 0.0495 moles
= Initial amount of the reactant = 0.7924 moles
n = number of half lives
Putting values in above equation, we get:
Taking log on both sides, we get
Answer:
4
Explanation:
Edg 2020
Related Questions
Which statement describes an alternate theory of acids and bases?(1) Acids and bases are both H+ acceptors.(2) Acids and bases are both H+ donors.(3) Acids are H+ acceptors, and bases are H+ donors.(4) Acids are H+ donors, and bases are H+ acceptors.
When dissolved in water, all acids willA. Form hydroxide ions B. have a negative eletrical charger C. conduct eletricity D. turn blue
Mendeleev’s principle of chemical periodicity states that when the elements are arranged according to their atomic numbers. This periodic law allows elements with similar properties to appear at regular intervals. Predict the group of elements and their number of valence electrons that will combine in a 2:1 ratio to with sodium. A)bromine, chlorine, iodine, 7 B)sulfur, selenium, polonium, 6 EliminateC)hydrogen, fluorine, potassium, 1 D)calcium, phosphorus, tellurium, 2
Many chemical and toxic substances used in modern industry are flammable or combustible. true/false
Answers
The correct option is False.
The first organic compound synthesized in the lab was urea. It was synthesized from silver cyanate and ammonium chloride. It is named Wöhler synthesis after the German chemist.
NH₄Cl + AgNCO → H₂NCONH₂
Urea was first synthesized in 1828 and its synthesis was the beginning of modern organic chemistry.
Hope this helps! :)
If you have 1.0 mole of each of the following compounds, which will have the most molecules?
Х
NI3 (nitrogen triiodide)
KCI (potassium chloride)
Lici (lithium chloride)
O C2H2 (ethyne)
O They all have the same number of molecules.
7
1/1 point
fn 35 moles of Iron (Fe)?
Answers
Answer:
6. They all have the same number of molecules.
7. 19.5 g
Explanation:
6. From Avogadro's hypothesis, we understood that 1 mole of any substance contains 6.02×10²³ molecules i.e
1 mole = 6.02×10²³ molecules
Considering the question given above, each compounds has just 1 mole. Thus, they will also have the same number of molecules.
7. Determination of the mass of iron (Fe)
Number of mole of Fe = 0.35 mole
Molar mass of Fe = 55.85 g/mol
Mass of Fe =?
Mass = mole × molar mass
Mass of Fe = 0.35 × 55.85
Mass of Fe = 19.5 g
Thus, the mass of 0.35 mole of iron (Fe) is 19.5 g
oxidation
hydrolysis
abrasion
Answers
Answer: The correct answer is oxidation.
Explanation:
Rust is a reddish-brown colored compound which is formed by the oxidation of Iron to form ferric oxide. The formula for this chemical compound is
Oxidation is defined as the reaction in which addition of oxygen takes place.
The reaction for the formation of rust is given by the equation, we get:
By Stoichiometry,
4 moles of iron metal reacts with 3 moles of oxygen gas to form 2 moles of ferric oxide.
Hence, the correct answer is oxidation.
1 m
1.000 mm
= 0.025 mm
1.000 mm
O 25.000 mm; because 25 m x = 25,000 mm
1 m
25.000 mm; because 25 m X
100 mm
= 2500 mm
1 m
O 0.025 mm; because 25 m x
1 m
100 mm
= 0.25 mm
Answers
Answer:
25000 mm: because 25 m × 1000 mm /1 m = 25000 mm
Explanation:
We can convert 25 m to millimetre (mm) by doing the following:
Recall:
1 m = 1000 mm
Therefore,
25 m = 25 m × 1000 mm /1 m = 25000 mm
25 m = 25000 mm
Thus, 25 m is equivalent to 25000 mm
Answers
Answer:
Explanation:
cience
Chemistry
Q&A Library
The following mechanism has been proposed for the gas-phase reaction of chloroform (CHCl3) and chlorine.Cl2 ⇌ 2Cl (fast, reversible) Cl + CHCl3 → HCl + CCl3 (slow) Cl + CCl3 → CCl4 (fast) What rate law does this mechanism predict?A)kG) [CHCl3]1/2M) [CCl3]2B) [Cl2]H) [CCl3]1/2N) [HCl]2C) [Cl]I) [HCl]1/2O) [Cl2]2D) [CHCl3]J) [Cl2]1/2P) [Cl]2E) [CCl3]K) [Cl]1/2 F) [HCl]L) [CHCl3]2
The following mechanism has been proposed for the gas-phase reaction of chloroform (CHCl3) and chlorine.Cl2 ⇌ 2Cl (fast, reversible) Cl + CHCl3 → HCl + CCl3 (slow) Cl + CCl3 → CCl4 (fast) What rate law does this mechanism predict?A)kG) [CHCl3]1/2M) [CCl3]2B) [Cl2]H) [CCl3]1/2N) [HCl]2C) [Cl]I) [HCl]1/2O) [Cl2]2D) [CHCl3]J) [Cl2]1/2P) [Cl]2E) [CCl3]K) [Cl]1/2 F) [HCl]L) [CHCl3]2
Question
Asked Oct 30, 2019
2468 views
The following mechanism has been proposed for the gas-phase reaction of chloroform (CHCl3) and chlorine.
Cl2 ⇌ 2Cl (fast, reversible)
Cl + CHCl3 → HCl + CCl3 (slow)
Cl + CCl3 → CCl4 (fast)
What rate law does this mechanism predict?
A)k G) [CHCl3]1/2 M) [CCl3]2
B) [Cl2] H) [CCl3]1/2 N) [HCl]2
C) [Cl] I) [HCl]1/2 O) [Cl2]2
D) [CHCl3] J) [Cl2]1/2 P) [Cl]2
E) [CCl3] K) [Cl]1/2
F) [HCl] L) [CHCl3]2
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Expert Answer
Step 1
The three step mechanism of the given reaction is,
CL2 dissociate to give chorine a fast and reverse reaction.
React with CHCL3 to give HCL and CCL3 a slow reaction
React with CL to give CCL4.
Step 2
Add equation (1), (2), and (3) to get the overall reaction.
The overall reaction is expressed as,
CL2 dissociate to give chorine a fast and reverse reaction.
React with CHCL3 to give HCL and CCL3 a slow reaction
React with CL to give CCL4.
Step 3
The chlorine atom produced in equation (1) is consumed in equation (3) and CCl3 a molecule is produced in equation (2) is consumed in equation (3).
CL react with CHCL3 to give a reversible reaction of HCL and CCL4.
True
False