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2 years ago

Using the half-life graph of cobalt-57, choose ALL the statements that are accurate.

Chemistry

1 answer:

Morgarella [4.7K]2 years ago

5 0

Answer: B) The half-life of Co-57 is 10 days

D) After twenty days have elapsed, about 25% of the Co-57 remains.

E) Scientists have an 8 gram sample of Co-57. After thirty days, 1 gram remains.

Explanation:

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Neutral atoms contain equal numbers of A protons and electrons. B protons and neutrons. C electrons and neutrons. D protons, ele

Verdich [7]

Answer:

For 1: The correct answer is Option A.

For 2: The correct answer is Option B.

For 3: The correct answer is Option C.

Explanation:

For 1:

Atomic number is defined as the number of electrons or number of protons that are present in a neutral atom. It is represented as Z.

Z = Atomic number = Number of electrons = Number of protons

Mass number is defined as the sum of number of protons and number of neutrons present in an atom. It is represented as A.

A = Mass number = Number of protons + Number of neutrons

Hence, the correct answer is Option A.

For 2:

The isotopic representation of an atom is: $_Z^A\textrm{X}$

where,

Z = Atomic number of the atom

A = Mass number of the atom

X = Symbol of the atom

We are given:

An isotopic representation of beryllium atom: $_4^9\textrm{Be}$

Thus, the number '4' represents the atomic number of beryllium, number '9' represents the mass number of beryllium atom.

Hence, the correct answer is Option B.

For 3:

In CO compound:

Mass of oxygen = 16 g

Mass of carbon = 12 g

In $CO_2$ compound:

Mass of oxygen = 32 g

Mass of carbon = 12 g

Thus, the ratio of mass of oxygen in $CO_2$ and CO is:

$CO_2:CO=32:16=2:1$

Hence, the correct answer is Option C.

3 0

3 years ago

Instrument used to measure atmospheric pressure

lisov135 [29]

Answer: barometer

Explanation:

7 0

2 years ago

Determine the pH of a 0.048 M hypochlorous acid (HClO) solution. Hypochlorous acid is a weak acid (Ka = 4.0 ✕ 10−8 M).

storchak [24]

pH of 0.048 M HClO is 4.35.

Explanation:

HClO is a weak acid and it is dissociated as,

HClO ⇄ H⁺ + ClO⁻

We can write the equilibrium expression as,

Ka = $$\frac{[H^{+}] [ClO^{-}] }{[HClO]}$

Ka = 4.0 × 10⁻⁸ M

4.0 × 10⁻⁸ M = $$\frac{x \times x }{0.048}$

Now we can find x by rewriting the equation as,

x² = 4.0 × 10⁻⁸ × 0.048

= 1.92 × 10⁻⁹

Taking sqrt on both sides, we will get,

x = [H⁺] = 4.38 × 10⁻⁵

pH = -log₁₀[H⁺]

= - log₁₀[ 4.38 × 10⁻⁵]

= 4.35

8 0

2 years ago

Which statement about scientific notation is true?

vladimir2022 [97]

Explanation:

the proper format for scientific notation the following conditions must be true

8 0

2 years ago

If there are three methyl groups on the same carbon, what is the prefix used?

Tanzania [10]

Answer:

tri

Explanation:

1-nothing

2-di

3-tri

- Hope that helps! Please let me know if you need further explanation.

6 0

2 years ago