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3 years ago

An element's atomic number is 7. How many protons would an atom of this element have?

Chemistry

2 answers:

rusak2 [61]3 years ago

8 0

well the atomic number is 7 the number of protons is also equal to 7 .

hope this helps

julsineya [31]3 years ago

5 0

If the atomic number is 7, the amount of protons is also 7.

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The half-life of cesium-137 is 30 years. suppose we have a 200-mg sample.

Assoli18 [71]

a) To find the mass after t years:

we will use this formula:

A = Ao / 2^n

when A =the amount remaining

and Ao = the initial amount

and n = t / t(1/2)

by substitution:

∴ A = 200 mg/ 2^(t/30y)

b) Mass after 90 y :

by using the previous formula and substitute t by 90 y

A = 200mg/ 2^(90y/30y)

∴ A = 25 mg

C) Time for 1 mg remaining:

when A= Ao/ 2^(t/t(1/2)

so, by substitution:

1 mg = 200 mg / 2^(t/30y)

∴2^(t/30y) = 200 mg by solving for t

∴ t = 229 y

7 0

4 years ago

1. what is an ethical concern about biotechnology

Anastasy [175]

Answer:

1. There are so many ethical concerns about biotechnology, some Ethical issues that arise from the application of modern biotechnologies include:

Discrimination of individuals because of their health or health history as a result of knowing their genetic information, minimizing harms while maximizing benefits, Interference with nature, privacy.

2. a. Plants (maize, rice)

b. Fish (GloFish)

3. For individuals, biotechnology has helped in the prevention and treatment of a wide range of diseases. For society, biotechnology saves time, improves the health and quality of food through a reduction in the use of pesticides and it can create new viruses and bacteria that cause diseases. Biotechnology could address global change since more genetically modified plants are grown.

8 0

3 years ago

Calculate the pH and fraction of dissociation ( α ) for each of the acetic acid ( CH 3 COOH , p K a = 4.756 ) solutions. A 0.002

marysya [2.9K]

Answer:

The degree of dissociation of acetic acid is 0.08448.

The pH of the solution is 3.72.

Explanation:

The $pK_a=4.756$

The value of the dissociation constant = $K_a$

$pK_a=-\log[K_a]$

$K_a=10^{-4.756}=1.754\times 10^{-5}$

Initial concentration of the acetic acid = [HAc] =c = 0.00225

Degree of dissociation = α

$HAc\rightleftharpoons H^++Ac^-$

Initially

At equilibrium ;

(c-cα) cα cα

The expression of dissociation constant is given as:

$K_a=\frac{[H^+][Ac^-]}{[HAc]}$

$1.754\times 10^{-5}=\frac{c\times \alpha \times c\times \alpha}{(c-c\alpha)}$

$1.754\times 10^{-5}=\frac{c\alpha ^2}{(1-\alpha)}$

$1.754\times 10^{-5}=\frac{0.00225 \alpha ^2}{(1-\alpha)}$

Solving for α:

α = 0.08448

The degree of dissociation of acetic acid is 0.08448.

$[H^+]=c\alpha = 0.00225M\times 0.08448=0.0001901 M$

The pH of the solution ;

$pH=-\log[H^+]$

$=-\log[0.0001901 M]=3.72$

3 0

3 years ago

What’s a giant hunk of rock and metal

Aleksandr-060686 [28]

Answer: “We live on a hunk of rock and metal that circles a humdrum star that is one of 400 billion other stars that make up the Milky Way Galaxy which is one of billions of other galaxies which make up a universe which may be one of a very large number, perhaps an infinite number, of other universes. That is a perspective on human life and our culture that is well worth pondering.”

― Carl Saga

Is this it mate?

5 0

3 years ago

A shampoo has a pH of 8.59. What is the [H3O+] in the shampoo?

Cerrena [4.2K]

Answer:

2.57 e-9

Explanation:

The formula is H3O=10^-Ph

10^-8.59=2.57 e-9

6 0

3 years ago