Answer:
The correct answer is 4.3635 g
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
Answer:
4.365g
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.
