Chemistry
08.08.2020 12:33
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Para cozinhar as batatas mais rápido segundo a cinética química devemos: a-( ) diminuir

Para cozinhar as batatas mais rápido segundo a cinética química devemos: a-( ) diminuir a temperatura
b-( ) aumentar a superfície de contato
c-( ) diminuir a pressão na panela
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hlhunter11p8f0o0
hlhunter11p8f0o0
4,4(25 marks)

a) 292.0 g

b) 1 ml

c) 0.29 %

Explanation:

a) The amount of NaCl can be calculated as follows:

m = C*V*M                                      

Where:

m: is the mass of NaCl =?

C: is the concentration of NaCl = 5M

V: is the volume = 1 L

M: is the molar mass of NaCl = 58.4 g/mol

m = C*V*M = 5 mol/L*1 L*58.4 g/mol = 292.0 g  

Hence, you need to take 292.0 g of NaCl to make 1 L of 5 M stock solution.

b) We need to use the following equation to find the quantity of stock solution that is needed to make 100 ml of 50 mM of NaCl:

C_{1}V_{1} = C_{2}V_{2}

Where:

C₁: is the initial concentration = 5 M

V₁: is the volume of the initial concentration =?          

C₂: is the concentration of the solution to prepare = 50 mM

V₂: is the volume of the solution to prepare = 100 ml

V_{1} = \frac{C_{2}V_{2}}{C_{1}} = \frac{50 \cdot 10^{-3} M*100 ml}{5 M} = 1 ml

Therefore, you need 1 ml of the stock solution to make 100 ml of 50 mM NaCl.

c) The % concentration of a 50 mM solution of NaCl is:

50 \cdot 10^{-3} \frac{mol}{1 L}*\frac{58.4 g}{1 mol}*0.1 L = 0.29 \%

Hence, the % concentration is 0.29 % (w/v).

I hope it helps you!

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