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4 years ago

What does the number next to isotopes signify?

1 answer:

6 0

The number next to isotopes signifies the sum of the number of protons plus the number of neutrons in the nucleus of an atom. An isotope is a version of an atom that has the same number of protons but different numbers of neutrons. Isotopes are very important in nuclear chemistry. A proton is a is a particle in the nucleus of an atom that has a positive charge. A neutron is also a particle in the nucleus of an atom, but it does not have an electric charge.

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How many moles of potassium nitrate are required to make 550 mL of a 2.1M solution?

stira [4]

Answer:

1.155 moles of potassium nitrate are required to make 550 mL of a 2.1M solution.

Explanation:

In a mixture, the chemical present in the greatest amount is called a solvent, while the other components are called solutes.

Molarity is a unit of concentration of a solution and indicates the amount of moles of solute that appear dissolved in each liter of the mixture. In other words, the Molarity (M) or Molar Concentration is the number of moles of solute that are dissolved in a given volume.

The Molarity of a solution is determined by the following expression:

$Molatity( M)=\frac{number of moles of solute}{Volume}$

Molarity is expressed in units ( $\frac{moles}{liter}$ ).

In this case:

Molarity= 2.1 M
number of moles of solute= ?
Volume= 550 mL= 0.550 L (being 1L=1000 mL)

Replacing:

$2.1 M= 2.1 \frac{moles}{liter} =\frac{number of moles of solute}{0.550 liters}$

Solving:

number of moles of solute= 2.1 M* 0.550 L

number of moles of solute= 1.155 moles

1.155 moles of potassium nitrate are required to make 550 mL of a 2.1M solution.

4 0

3 years ago

How many moles in 2 h2o molecules

alexandr1967 [171]

Answer:

2 molecules of water represents 3.32 x 10^-24 moles of water.

Explanation:

To find the solution to this problem, you have to use the concept of Avogadro´s number, that is in 1 mol of any element o compound there are 6.022 x 10^23 molecules. Then,

1 mol H2O ------------- 6.022 x 10^23 molecules

x= 3.32 x 10^-24 ---- 2 molecules.

2 molecules of water represents 3.32 x 10^-24 moles of water.

5 0

3 years ago

If 29.4 mL of ethanol is dissolved in water to make 359 mL of solution, what is the concentration expressed in volume/volume % o

Sveta_85 [38]

Answer: $8.2\%$

Explanation:- Volume percentage is the ratio of volume of solute to the volume of solution defined in terms of percentage.

${\text {volume percentage}}=\frac{\text {volume of solute}}{\text {volume of solution}}\times 100\%$

Given: volume of solute = 29.4 ml

Volume of solution= 359 ml

${\text {volume percentage}=\frac{29.4}{359}\times 100\%=8.2\%$

6 0

4 years ago

Metal plating is done by passing current through a metal solution. For example, an item can become gold plated by attaching the

Norma-Jean [14]

Answer:

9.18g

Explanation:

Step 1: Write the reduction half-reaction

Au³⁺(aq) + 3 e⁻ ⇒ Au(s)

Step 2: Calculate the mass of gold is produced when 15.0A of current are passed through a gold solution for 15.0min

We will use the following relationships:

1 min = 60 s

1 A = 1 C/s

1 mole of electrons has a charge of 96486 C (Faraday's constant).

1 mole of Au is produced when 3 moles of electrons circulate.

The molar mass of Au is 196.97 g/mol.

The mass of gold produced is:

$15.0 min \times \frac{60s}{1 min} \times \frac{15.0C}{1s} \times \frac{1 mol e^{-} }{96486C} \times \frac{1molAu}{3 mol e^{-} } \times \frac{196.97gAu}{1molAu} = 9.18gAu$

3 0

3 years ago

What happens to water molecules when they are heated?

stealth61 [152]

Temperature causes water molecules to move more quickly, because each individual molecule has more energy as it gets hotter .

So, the answer is A.

6 0

4 years ago

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