Molar mass, mass and moles
Particles and moles
Mass Percent Composition
Dilution
Molarity
100
To find number of moles from number of grams, you would use ______
molar mass of a molecule
100
To convert between from number of moles and Number of particles, you would use ______
Avagadro's Number=6.022 x1023
100
What is the first step you need to do to figure out the percent composition by mass of a molecule?
- Find the molar mass of all the elements in the compound in grams per mole. *the following steps are below*
- Find the molecular mass of the entire compound.
- Divide the component's molar mass by the entire molecular mass.
- You will now have a number between 0 and 1. Multiply it by 100% to get percent composition.
100
What is the formula for Dilution?
M1 = Initial Molarity
V1= Initial Volume
M2= Final Molarity
V2=Final Volume
100
The correct definition for molarity is ______divided by ___.
moles solute/L solution
200
What is the molar mass of H2S (in g/mol)?
34.086 g/mol
*add molar mass of 2 H and 1 S
200
How many mol of hydrogen atoms are in 0.203 mol of Fe(OH)3 ?
0.609 mol
*Take 0.203 and multiply by the # of H atoms (3)/ # of Entire molecule (1)
200
A sample of a compound is decomposed and found to contain 9.01 g of S and 4.50 g of O. What is the empirical formula of this compound?
SO
*1st step: take S and O and convert each to mols
2nd step: You will see it comes out to 0.28 mol S and 0.28 mol O which is 1:1 ratio
200
You have a concentrated solution of compound Z. You take a small volume of this solution, and add it to a much larger volume of water to make a new solution.
Which of the following is true about the new solution?
Group of answer choices
A. It is less concentrated than the original solution
B. It is more concentrated than the original solution
C. It has the same concentration as the original solution
A. It is less concentrated than the original solution
200
What is the molarity of a solution that has 1.75 mol of sucrose in a total of 4.85 L of solution?
0.3608 M
*1.75 mols/ 4.85 L
300
What is the mass of a single atom of krypton (Kr)?
1.39 x 10-22 g
*first take molar mass then divide by avagadro's number
300
You have 8.7319 x1023 particles of Hydrogen. How many moles are there?
1.45 Moles
*divide by avagadro's number
300
What is the mass percent of Fe in iron(II) bromide ( FeBr2 ) ?
25.9% Fe
*First find molar mass of Fe and Br2
Then divide MM of Fe by total molar mass.
300
You have a concentrated solution of 5.00 M NaOH. If you dilute 98.5 mL of this solution with water to a final volume of 2.00 L, what is the molarity of the diluted solution?
0.246 M
*Remember to convert mL to L
*Plug into dilution formula
300
A 2.00 M solution contains 3.50 mol of the solute. What is the volume (in L) of this solution?
1.75 L
*Take 3.5 mol and divide by 2 M
400
What is the mass (in g) of 0.935 mol of aluminum?
25.2 g
*You would take 0.935 mol and multiply by the molar mass of Al, which is 26.98 g/mol
400
How many protons are in 7.91 x 10-22 g of F?
226
*You will need to convert from Mass to moles to particles to protons
400
A compound was decomposed and determined to be 55.16 % C, 8.10 % H and 36.74 % O by mass. What is the subscript for H in the empirical formula for this compound?
7 (H7)
*Review Determining Formula From Percent Composition video if this is difficult
*Tip:
1. Assume 100g sample then convert to mols.
2. From moles, divide each by smallest number (0.02296 mol O)
3. Multiply all by 2
400
You have a concentrated solution of 5.00 M NaOH. If you dilute 135.5 mL of this solution with water to a final volume of 2.00 L, what is the molarity of the diluted solution?
0.339 M
400
What volume (in mL) of 5.00 M HCl must diluted to a final volume of 1.50 L to make a solution with a final concentration of 0.450?
135 mL
*Remember that equation is asking for answer in mL so convert 0.135 L to 135 mL
500
How many mol of hydrogen atoms are in 0.203 mol of Fe(OH)3 ?
0.609
500
You have measured out 75.00 g of Mg(OH)2 (formula weight: 58.33 g/mol) to make a solution. What must your final volume be (in L) if you want a solution made from this mass of Mg(OH)2 to have concentration of 0.245 M?
5.25 L
*Find moles from 75.00g and 58.33 g/mol
might help to set up equation like L=Moles/Molarity