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2 years ago

How much sodium chloride (NaCl) would need to be added to 750 milliliters of water to make a 15% solution?

Chemistry

1 answer:

oee [108]2 years ago

5 0

Answer: 6.58g

Explanation: We are to find the mass of NaCl that can produce 15% solution in a 750ml

STEP 1:

the reaction moles

NaCl + H2O = NaOH + HCl

Therefore 1mole of NaCl reacts with 1mole of H2O

STEP 2:

convert 750ml to liter

750ml × 1L/1000ml = 0.750L

STEP3 :

convert percentage concentration to mol/L

15% = 0.15mol/L

STEP 4:

find the mole

Mole= concentration× volume

0.15mol/L × 0.75L =0.1125mol

STEP 5 :

Find the mass

Mass = mole × molar mass

The molecular mass of NaCl is 23+35.5= 58.5g/mol

Therefore:

0.1125mol × 58.5g/mol = 6.58g

Approximately: 6.6g

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What is the longest wavelength in the Balmer series? (Hint: the Rydberg constant for Hydrogen is 1.096776×107 1/m, and the Balme

boyakko [2]

Answer: The longest wavelength of light is 656.5 nm

Explanation:

For the longest wavelength, the transition should be from n to n+1, where: n = lower energy level

To calculate the wavelength of light, we use Rydberg's Equation:

$\frac{1}{\lambda}=R_H\left(\frac{1}{n_i^2}-\frac{1}{n_f^2} \right )$

Where,

$\lambda$ = Wavelength of radiation

$R_H$ = Rydberg's Constant = $1.096776\times 10^7m^{-1}$

$n_f$ = Higher energy level = $n_i+1=(2+1)=3$

$n_i$ = Lower energy level = 2 (Balmer series)

Putting the values in above equation, we get:

$\frac{1}{\lambda }=1.096776\times 10^7m^{-1}\left(\frac{1}{2^2}-\frac{1}{3^2} \right )\\\\\lambda =\frac{1}{1.5233\times 10^6m^{-1}}=6.565\times 10^{-7}m$

Converting this into nanometers, we use the conversion factor:

$1m=10^9nm$

So, $6.565\times 10^{-7}m\times (\frac{10^9nm}{1m})=656.5nm$

Hence, the longest wavelength of light is 656.5 nm

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