Question

Dealing with a 0.150 M Co(NO3)2•6H2O. Determine the number of grams of Co(NO3)2•6H2O that you would need to weigh out in order to prepare 100.00 mL of the solution

Answer 1

4.365g

Step-by-step explanation:

We'll begin by calculating the number of mole of Co(NO3)2•6H2O present in 100mL of 0.150 M Co(NO3)2•6H2O solution. This is illustrated below:

Molarity = 0.150M

Volume of solution = 100mL

Recall: 1000mL = 1L

Therefore, 100mL = 0.1L

Mole of solute (Co(NO3)2•6H2O) =?

Molarity is simply mole per unit litre of solution. It is represented mathematically as:

Molarity = mole /Volume

Mole = Molarity x Volume

Mole of Co(NO3)2•6H2O = 0.15x0.1

Mole of Co(NO3)2•6H2O = 0.015mol

Now, we need to convert 0.015mol to grams in order to obtain the desired result. This is illustrated below:

Mole of Co(NO3)2•6H2O = 0.015mol

Molar Mass of Co(NO3)2•6H2O = 59 + 2[14 + (16x3)] + 6[(2x1) + 16] = 59 + 2[14 + 48] + 6[2 + 16] = 59 + 2[62] + 6 [18] = 59 + 124 + 108 = 291g/mol

Mass of Co(NO3)2•6H2O =?

Mass = number of mole x molar Mass

Mass of Co(NO3)2•6H2O = 0.015 x 291

Mass of Co(NO3)2•6H2O = 4.365g

Therefore, 4.365g of Co(NO3)2•6H2O is needed to prepare 100mL of 0.150 M Co(NO3)2•6H2O solution.

Answer 2

The correct answer is 4.3635 g

Step-by-step explanation:

First, we have to calculate the molecular weight of the solute (Co(NO₃)₂•6H₂O). For this, we obtain the molar mass of the elements from the Periodic Table (Co, N, O and H) and calculate as follows:

MW(Co(NO₃)₂•6H₂O) = (1 x MM(Co)) + (2 x MM(N)) + ((2 x 3) x MM(O)) + ((6 x 2) x (MM(H)) + (6 x (MM(O)))

= (58.9 g/mol) + (2 x (14 g/mol)) + (6 x 16 g/mol) + (12 x 1 g/mol) + 6 x (16 g/mol)

= 290.9 g/mol

We have a solution 0.150 M Co(NO₃)₂•6H₂O, so we can convert from mol/L to g/L if we multiply the concentration by the molecular weight as follows:

0.150 mol/L x 290.9 g/ 1 mol = 43.635 g/L

Finally, we have to prepare a 100 ml solution. This volume is equal to 0.1 L, so we multiply the concentration in g/L by the volume in L and we obtain the mass we need to weigh:

mass = 43.635 g/L x 0.1 L = 4.3635 g