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tia_tia [17]
3 years ago
6

A laboratory technician combined sodium hydroxide with excess iron(II) nitrate. A reaction took place according to this chemical

equation: 2NaOH + Fe(NO3)2 → NaNO3 + Fe(OH)2.
The reaction produced 3.70 grams of iron(II) hydroxide.

Assuming the reaction came to completion, what was the initial mass of sodium hydroxide? Use the periodic table.

A. 1.6 g
B. 2.0 g
C. 3.3 g
D. 4.0 g
Chemistry
1 answer:
Whitepunk [10]3 years ago
8 0

 The initial  mass  of sodium hydroxide  is  3.3 g (answer C)

 <u><em>calculation</em></u>

Step 1 : find the  moles of iron (ii) hydroxide (  Fe(OH)₂

moles =  mass÷  molar mass

from periodic table the  molar mass of Fe(OH)₂  = 56 + [16 +1]2  = 90 g/mol

moles  is therefore = 3.70 g÷ 90 g/mol = 0.041 moles

Step 2:  use the mole ratio to  calculate the moles of  sodium hydroxide (NaOH)

   from given equation  NaOH : Fe(OH)₂    is 2 :1

therefore the moles of NaOH = 0.041 x 2 = 0.082 moles

Step 3: find  mass of NaOH

mass = moles x molar mass

from the periodic table the  molar mass of NaOH = 23 +16 +1  = 40 g/mol

mass  = 0.082  moles x 40 g/mol = 3.3 g ( answer C)


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Answer:

pH = 3; acidic

Explanation:

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pH = -log[H+]

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pH = -log(0.0010)

pH = 3

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Ultraviolet radiation and radiation of shorter wavelengths can damage biological molecules because they carry enough energy to b
DIA [1.3K]
<h3>Answer:</h3>

Longest wavelength = 343.7 nm

<h3>Solution and Explanation:</h3>

In this question we need to first use the concept of energy of a photon.

Energy of a photon, E, is given by the formula, E = hf, where h is the plank's constant, f is the frequency.

But since, f is given by dividing speed, c, by wavelength, λ, then;

E = hc/λ

We are given 348 kJ/mol required to break carbon-carbon bonds.

We know that; 1 mole of bonds = 6.022 × 10^23 bonds.

We are required to find the longest wavelength with enough energy to break the C-C bonds.

This can be worked out in simple steps:

Step 1:  Energy required to break one bond (kJ/bond)

1 mole of bonds = 6.022 × 10^23 bonds.

Therefore;

348 kJ = 6.022 × 10^23 bonds.

Thus;

1 bond = 348 kJ ÷ 6.022 × 10^23 bonds.

           =  5.778 x 10^-22 kJ

But; 1000 joules = 1 kJ

Hence; energy per bond =  5.778 x 10^-19 Joules

Step 2: Energy per photon

Breaking one bond requires energy equivalent to energy of a photon.

Therefore;

1 photon = 5.778 x 10^-19 Joules

              = 5.778 x 10^-19 J/photon

Step 3: Calculating the wavelength

From the equation of energy of a photon;

E = hc/λ

h is the plank's constant = 6.626 × 10^-34 J/s

c is the speed of light in vacuum = 2.9998 × 10^8 m/s

E is the energy of a photon =  5.778 x 10^-19 Joules

Therefore, making λ (wavelength) the subject;

wavelength = \frac{hc}{E}

= \frac{(6.626 . 10^{-34})(92.9998.10^8) }{(5.778 .10^{-19} )}

= 3.437. 10^{-7} m

       = 3.437 x 10^-7 m

But; 1 nm = 10^-9 m

Thus;

wavelength = 343.7 nm

Therefore, the longest wavelength of the radiation will be 343.7 nm

5 0
3 years ago
A large piece of cork has a density of 0.251 g/cm3 and a volume of 1000.0 cm3. Calculate the mass of the cork.
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Answer:

<h2>251 g</h2>

Explanation:

The mass of a substance when given the density and volume can be found by using the formula

mass = Density × volume

From the question we have

mass = 0.251 × 1000

We have the final answer as

<h3>251 g</h3>

Hope this helps you

4 0
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