Questions on making Solutions!?

Question

1. Two hydrogen atoms can be combined with one atom of oxygen to make water

(H2O). If you had 16 grams of oxygen atoms, how many grams of hydrogen

atoms would you need to react with all of the oxygen atoms?

2. A 1 molar (1 M) solution is one in which there is one mole solute in 1 liter of water.

How many glucose atoms would be present in this solution?

3. If you wanted to make one liter of a one molar glucose solution (C6H12O6), how

many grams of glucose would you need? What is this equal to in milligrams /

Liter? In mg/ml?

4. How many grams of glucose would you need to make one liter of a 0.5 M

solution? A 0.1 M solution? A 3 M solution?

5. How many grams of glucose would you need to make 500 ml (0.5 L) of a 1 M

glucose solution? 100 ml?

Answer 1

1. First write out the chemical reaction that you've given

2H + 0.5O2 --> H2O

If you have 16 grams of oxygen, how many grams of hydrogen do you need?

(16 g O)(1 mol O/ 16 g O)(2 mol H/0.5 mol O)(1 g H/1 mol H) = 4 g H

2. The molecular formula of glucose is C6H12O6

The molar mass of glucose is approximately 180 g/mol

Also recall Avogadro's number, 6.022 x 10^23

( mol C6H12O6/ 180 g C6H12O6)(6.022 x 10^23 atoms/ mole) = 3.35 x 10^21 C6H12O6 atoms

3. if you want to make 1 L of a 1 M solution you would need

(L)(mol/L)(180 g/mol) = 180 g C6H12O6

in mg/L:

(180 g)(1000 mg/g) = 1.8 x 10^5 mg/L

in mg/mL:

(1.8 x 10^5 mg/L)(L/1000 mL) = 180 mg/mL

4.

general plan:

(L)(mol/L)(180 g/mol)

0.5M:

(L)(0.5 mol/L)(180 g/ mol) = 90 g

0.1M:

(L)(0.1 mol/L)(180 g/ mol) = 18 g

3M:

(L)(3 mol/ L)(180 g/ mol) = 540 g

5. Same plan as the previous problems

(.5 L)( mol/L)(180 g/mol) = 90 g

100 mL = 0.1 L

(0.1L)(mol/L)(180 g/ mol) = 180 g

6. if you have 1 L and if you put an equal amount into all 4 flasks there is 0.25 L of 1M glucose in each flask.

I think we need the density of glucose to find out how many atoms of glucose are present in each flask.

0.25 L x density x (mol/ 180 g) x 6.022 x 10^23 atoms/mol = ? atoms of glucose

look up the density of glucose in a book or online and plug it into the equation above and solve.

(1 mol/ L)(180 g/ mol) = 180 g/ l of glucose per flask