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shepuryov [24]
2 years ago
6

A sample of radioactive material starts with 80 grams. After 3 half-lives have passed, how much radioactive sample remains?

Chemistry
1 answer:
Elanso [62]2 years ago
5 0

Answer:

After 3 half lives 10 g of radio active material left.

Explanation:

Given data:

Total amount of radio active material = 80 g

Amount left after 3 half lives = ?

Solution:

At time zero = 80 g

At first half life = 80 g/2 = 40 g

At 2nd half life = 40 g/2 = 20 g

At 3rd half life = 20 g/2 = 10 g

Thus, after 3 half lives 10 g of radio active material left.

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How many moles of KCl will be<br> produced from 15.0 g of KClO3?
slega [8]

Answer:

0.12 mol KCl

Explanation:

2 KClO3 (s)   2 KCl (s) + 3 O2 (g)

15 g                x mol

x g KCl = 15 g KClO3 x[ (1 mol KClO3)/ (122.5 g KClO3) ] x [(2 mol KCl)/ (2 mol KClO3)]

x g KCl = 0.12 mol KCl

7 0
2 years ago
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Which statement best describes how an ionic bond forms?
maxonik [38]
<span>The question says,'which statement best describes how an ionic bond forms. The correct option is A. Ionic bonds are formed as a result of complete transfer of electrovalence electrons from one atom to another. The atom that donate the electron become a positively charged ion while the atom that received the atom become a negatively charged ion.</span>
4 0
2 years ago
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Plasmid DNA and a gene of interest are cut with the enzyme PpuMI. Write a possible sequence of bases for the sticky end of the g
nasty-shy [4]

Answer:

5' RG        GWCCY 3'

3' YCCWG        GR 5'

Explanation:

The enzyme PpuMI is a restriction endonuclease enzyme, it has a specific recognition site where it cut the DNA. The source of the enzyme is from ​​an E. coli strain that carries the PpuMI gene from Pseudomonas putida (R. Morgan).

The enzyme PpuMI recognizes specific sequence with palindrome arrangement. It target the sequence 5' RGGWCCY 3'

target Sequence: 5' RGGWCCY 3'

                            3' YCCWGGR 5'

The enzyme cleavage point is at:

5' RG^GWCCY 3'

3' YCCWG^GR 5'

The product of the cleavage will give a sticky end Cleavage:

5' RG        GWCCY 3'

3' YCCWG        GR 5'

Note: R stands for purines (adenine and guanine). Y stands for pyrimidines (cytosine, thymine, and uracil). And W represents adenine or thymine.

5 0
2 years ago
analysis of a compound indicates that it contains 1.04 grams K 0.70 g Cr and 0.86 g O. Find its empirical formula
MrMuchimi
1.04gK*1molK/39.01g K= 0.0267 mol K
0.70gCr*1mol/52.0g Cr = <span>0.0135 mol Cr   
0.86 gO* 1 mol/16.0 g O = 0.0538 mol O
</span>0.0267 mol K/0.0135 = 2 mol K
0.0135 mol Cr  /0.0135= 1 mol Cr
 0.0538 mol O/0.035= 4 mol Cr
K2CrO4
6 0
2 years ago
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A 0.72-mol sample of PCl5 is put into a 1.00-L vessel and heated. At equilibrium, the vessel contains 0.40 mol of PCl3(g) and 0.
Sonja [21]

Answer:

Equilibrium constant for PCl_5 is 0.5

Equilibrium constant for decomposition of NO_2 is 1.79 \times 10^{-14}

Explanation:

PCl_5 dissociates as follows:

                    PCl_5 \rightleftharpoons PCl_3+Cl_2

initial          0.72 mol     0         0

at eq.     0.72 - 0.40   0.40      0.40

Expression for the equilibrium constant is as follows:

k=\frac{[PCl_3][Cl_2]}{[PCl_5]}

Substitute the values in the above formula to calculate equilibrium constant as follows:

k=\frac{[0.40/1][0.40/1]}{0.32/1} \\=\frac{0.40 \times 0.40}{0.32} \\=0.5

Therefore, equilibrium constant for PCl_5 is 0.5

Now calculate the equilibrium constant for decomposition of  NO_2

It is given that 3.3 \times 10^{-3} \% is decomposed.

NO_2 decomposes as follows:

                                  2NO_2 \rightleftharpoons 2NO + O_2

initial                            1.0 M       0           0

at eq. concentration of  NO_2   is:

[NO_2]_{eq}=1-(0.000066) = 0.999934\ M

[NO]_{eq}=6.6 \times 10^{-5}\ M

[O_2]_{eq}=3.3\times 10^{-5} = 3.3\times 10^{-5}\ M      

Expression for equilibrium constant is as follows:

K=\frac{[NO]^2[O_2]}{[NO_2]^2}

Substitute the values in the above expression

K=\frac{[6.6\times 10^{-5}]^2[3.3 \times 10^{-5}]}{[0.999934]^2} \\=1.79\times 10^{-14}

Equilibrium constant for decomposition of NO_2 is 1.79 \times 10^{-14}

8 0
2 years ago
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