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3 years ago

A chemist needs 0.550 mol selenium for a reaction. What mass of selenium should a chemist use?

Chemistry

1 answer:

-BARSIC- [3]3 years ago

4 0

Answer:

The chemist would require to use 43.43 grams.

Explanation:

In order to solve this problem we need to know how much do 0.550 moles of selenium weigh. To do that we use selenium's molar mass and multiply it by the given number of moles:

0.550 mol * 78.96 g/mol = 43.43 g

The chemist would require to use 43.43 grams.

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Water molecules are highly _______ and are always _________.

anyanavicka [17]

Water molecules are highly packed and are always near each other.

7 0

2 years ago

Identify all the physical properties of a base.

KiRa [710]

Answer:

Bases are ionic compounds that produce negative hydrogen ions (OH⁻) when dissolved in water.
An example of a base is Sodium Hydroxide (NaOH).
Bases have a bitter taste.
Bases feel slippery.
Bases conduct electricity when dissolved in water.
Bases change litmus paper from red to blue in colour.
They react with acids to form a salt and water, this process is called neutralisation.
The pH of bases ranges from 8-14.
Turns phenolphthalein pink.

Hope this helps!

7 0

3 years ago

Which one of the following statements is not true concerning 2.00 L of a 0.100 M solution of Ca3(PO4)2?

Len [333]

Answer: The correct answer is Option B.

Explanation:

To calculate the molarity of solution, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}$ .......(1)

For A:

Molarity of calcium phosphate solution = 0.100 M

Volume of solution = 2.00 L

Putting values in equation 1, we get:

$0.100M=\frac{\text{Moles of }Ca_3(PO_4)_2}{2.00}\\\\\text{Moles of }Ca_3(PO_4)_2=(0.100mol/L\times 2.00L)=0.200mol$

Moles of calcium phosphate = 0.200 moles

For B:

1 mole of calcium phosphate contains 3 moles of calcium atoms, 2 moles of phosphate atoms and 8 moles of oxygen atoms.

So, 0.200 moles of calcium phosphate will contain = $(8\times 0.200)=1.6$ moles of oxygen atoms.

Moles of oxygen atoms = 1.6 moles

For C:

Molarity of calcium phosphate solution = 0.100 M

Volume of solution = 1.00 L

Putting values in equation 1, we get:

$0.100M=\frac{\text{Moles of }Ca_3(PO_4)_2}{1.00}\\\\\text{Moles of }Ca_3(PO_4)_2=(0.100mol/L\times 1.00L)=0.100mol$

Moles of calcium ions = $(0.100\times 3)=0.300$ moles

For D:

Molarity of calcium phosphate solution = 0.100 M

Volume of solution = 5.00 L

Putting values in equation 1, we get:

$0.100M=\frac{\text{Moles of }Ca_3(PO_4)_2}{5.00}\\\\\text{Moles of }Ca_3(PO_4)_2=(0.100mol/L\times 5.00L)=0.500mol$

Moles of phosphorus atoms = $(0.500\times 2)=1.00$ moles

According to mole concept:

1 mole of a compound contains $6.022\times 10^{23}$ number of atoms

Number of phosphorus atoms in 0.500 moles of calcium phosphate will be = $(1.00\times 6.022\times 10^{23})=6.022\times 10^{23}$

For E:

1 mole of calcium phosphate contains 3 moles of calcium ions and 2 moles of phosphate ions.

So, 0.200 moles of calcium phosphate will contain = $(3\times 0.200)=0.600$ moles of calcium ions

Moles of calcium ions = 0.600 moles

Hence, the correct answer is Option B.

6 0

2 years ago

Are protons positive and neutrons neutral

Elis [28]

Answer: Yes, they're neutral.

3 0

3 years ago

A 1.5 M solution of NaOH was made in a laboratory. If the solution made had a volume of 4.5 L, how many grams of NaOH were added

Crank

Answer:

270g

Explanation:

Given parameters:

Concentration of NaOH = 1.5M

Volume = 4.5L

Unknown

Mass of NaOH added = ?

Solution:

To solve the problem, we need to find the number of moles of the NaOH first;

Number of moles = concentration x volume

Number of moles = 1.5 x 4.5 = 6.75mol

Now;

Mass = Number of moles x molar mass

Molar mass of NaOH = 23 + 16 + 1 = 40g/mol

Mass = 6.75 x 40 = 270g

6 0

2 years ago