If a scientist has an initial sample of 200 g of carbon-14, how much will remain after one half-life?

Boron has an atomic mass of 11. How many neutrons are in its nucleus? Use the periodic table if you wish.

makvit [3.9K]

<u>Answer:</u> The number of neutrons in boron are 6.

<u>Explanation:</u>

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

Atomic number = number of protons = number of electrons

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

Mass number = Number of neutrons + Number of protons.

We are given:

Mass number = 11

Atomic number of boron = 5

Number of neutrons = Mass number - Atomic number = 11 - 5 = 6

Hence, the number of neutrons in boron are 6.

4 0

3 years ago

Suppose 0.245 g of sodium chloride is dissolved in 50. mL of a 18.0 m M aqueous solution of silver nitrate.

Bezzdna [24]

Answer:

$\large \boxed{\text{ 0.066 mol/L}}$

Explanation:

We are given the amounts of two reactants, so this is a limiting reactant problem.

1. Assemble all the data in one place, with molar masses above the formulas and other information below them.

Mᵣ: 58.44

NaCl + AgNO₃ ⟶ NaNO₃ + AgCl

m/g: 0.245

V/mL: 50.

c/mmol·mL⁻¹: 0.0180

2. Calculate the moles of each reactant

$\text{Moles of NaCl} = \text{245 mg NaCl} \times \dfrac{\text{1 mmol NaCl}}{\text{58.44 mg NaCl}} = \text{4.192 mmol NaCl}\\\\\text{ Moles of AgNO}_{3}= \text{50. mL AgNO}_{3} \times \dfrac{\text{0.0180 mmol AgNO}_{3}}{\text{1 mL AgNO}_{3}} = \text{0.900 mmol AgNO}_{3}$

3. Identify the limiting reactant

Calculate the moles of AgCl we can obtain from each reactant.

From NaCl:

The molar ratio of NaCl to AgCl is 1:1.

$\text{Moles of AgCl} = \text{4.192 mmol NaCl} \times \dfrac{\text{1 mmol AgCl}}{\text{1 mmol NaCl}} = \text{4.192 mmol AgCl}$

From AgNO₃:

The molar ratio of AgNO₃ to AgCl is 1:1.

$\text{Moles of AgCl} = \text{0.900 mmol AgNO}_{3} \times \dfrac{\text{1 mmol AgCl}}{\text{1 mmol AgNO}_{3}} = \text{0.900 mmol AgCl}$

AgNO₃ is the limiting reactant because it gives the smaller amount of AgCl.

4. Calculate the moles of excess reactant

Ag⁺(aq) + Cl⁻(aq) ⟶ AgCl(s)

I/mmol: 0.900 4.192 0

C/mmol: -0.900 -0.900 +0.900

E/mmol: 0 3.292 0.900

So, we end up with 50. mL of a solution containing 3.292 mmol of Cl⁻.

5. Calculate the concentration of Cl⁻

$\text{[Cl$^{-}$] } = \dfrac{\text{3.292 mmol}}{\text{50. mL}} = \textbf{0.066 mol/L}\\\text{The concentration of chloride ion is $\large \boxed{\textbf{0.066 mol/L}}$}$

8 0

3 years ago

Who discovered the electron?

Sedbober [7]

J.J. Thomson discovered the electron 1897

3 0

3 years ago

Which technology would be the most useful in predicting an eruption from an undersea volcano and why

sveticcg [70]

Answer: Infrasound because sound waves travel easily through water to accessible buoys.

Explanation: its installation: underwater microphones hung from buoys near a volcano. how it works: senses low-frequency sound waves near a volcano. Since in its installation it specifies that it has UNDERWATER microphones and the question asks in predicting an eruption from an UNDERSEA volcano, that makes perfect sense.

8 0

3 years ago

Hello guys sorry for spamming again but I have to do this whole thing and the end of trimester for my school is today so I need

Aloiza [94]

Answer:

all you need if yo look up and say do plants grow without soil but yes they can grow without soil but they cannot grow without the necessities that soil provides.

4 0

3 years ago