Answer:
2.25g of NaF are needed to prepare the buffer of pH = 3.2
Explanation:
The mixture of a weak acid (HF) with its conjugate base (NaF), produce a buffer. To find the pH of a buffer we must use H-H equation:
pH = pKa + log [A-] / [HA]
<em>Where pH is the pH of the buffer that you want = 3.2, pKa is the pKa of HF = 3.17, and [] could be taken as the moles of A-, the conjugate base (NaF) and the weak acid, HA, (HF). </em>
The moles of HF are:
500mL = 0.500L * (0.100mol/L) = 0.0500 moles HF
Replacing:
3.2 = 3.17 + log [A-] / [0.0500moles]
0.03 = log [A-] / [0.0500moles]
1.017152 = [A-] / [0.0500moles]
[A-] = 0.0500mol * 1.017152
[A-] = 0.0536 moles NaF
The mass could be obtained using the molar mass of NaF (41.99g/mol):
0.0536 moles NaF * (41.99g/mol) =
<h3>2.25g of NaF are needed to prepare the buffer of pH = 3.2</h3>
In order to convert the moles of a substance to grams, you will need to multiply the mole value of the substance by its molar mass. More commonly written for this application as: where, is the molar mass of the substance.
Hope this helped
:)
Answer:
percent error = - 99.134 %
Explanation:
Given data:
measured length = 1.85 cm
accepted or given value length = 2.15 m
percent error = ?
Solution:
First of all we will convert the length in meter into cm.
1 meter = 100 cm
2.15 × 100 = 215 cm
Formula:
percent error = (measured value - accepted value/ accepted value) × 100%
Now we will put the values in equation
percent error = (1.85 cm - 215 cm/ 215 cm) × 100%
percent error = -0.9914 × 100%
percent error = - 99.134 %
How many electrons does each element have to lose again to achieve a noble gas electron configuration?
Answer:
Explanation:
Each element will gain or lose electron to attain the octet of the noble gases in their outer shell electrons.
- Most metals in group 1 and 2 will lose 1 and 2 electrons apiece to attain a noble configuration.
- Non-metals are typically electronegative and will gain considerable amount of electrons to complete their octet.
- Halogens will need one electron to complete their own out shell configuration.
Elements will gain or lose an amount of electron that will make it resemble noble gases.
