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3 years ago

14

In which group do all atoms have two valence electrons in the ground state?

1 answer:

Nitella [24]3 years ago

5 0

<span>Alkaline Earths hope this helps

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The ka values for several weak acids are given below. which acid (and its conjugate base) would be the best buffer at ph = 8.0?

Pie

One of the best buffer choice for pH = 8.0 is Tris with Ka value of 6.3 x 10^-9.

To support this answer, we first calculate for the pKa value as the negative logarithm of the Ka value:
pKa = -log Ka

For Tris, which is an abbreviation for 2-Amino-2-hydroxymethyl-propane-1,3 -diol and has a Ka value of 6.3 x 10^-9, the pKa is
pKa = -log Ka
= -log (6.3x10^-9)
= 8.2

We know that buffers work best when pH is equal to pKa:
pKa = 8.2 = pH

Therefore Tris would be a best buffer at pH = 8.0.

7 0

4 years ago

Read 2 more answers

PLEASE HELP ME WITH MY CHEM TEST

fgiga [73]

Answer:

8. 0.96

9. d

10b

11. 3

12 d

Explanation:

4 0

3 years ago

How are isotopes of the same chemical element alike? How are they different?

Stella [2.4K]

<u>Answer:</u> The atomic mass of these species is different and atomic number remains same.

<u>Explanation:</u>

Isotopes are the chemical species of the same element having different number of neutrons.

Atomic number is equal to the number of protons or electrons present in that element.

Atomic Number = Number of electrons = Number of protons

Atomic mass is defined as the sum of number of protons and neutrons contained in an atom.

Atomic Mass = Number of protons + Number of neutrons

For isotopes, as the number of neutrons differ, the atomic mass also differs.

For Example: Carbon has 3 naturally occurring isotopes: $_6^{12}\textrm{C},_6^{13}\textrm{C}\text{ and }_6^{14}\textrm{C}$ . The atomic number remains the same but atomic mass differs.

Hence, for isotopes, the atomic mass of these species is different and atomic number remains same.

6 0

3 years ago

You dissolve 8.65 grams of lead(l) nitrate in water and then you add 2 50 grams of aluminum. This reaction occurs 2AI(S)+ 3Pb(NO

olga55 [171]

<u>Answer:</u> The theoretical yield of solid lead comes out to be 5.408 grams.

<u>Explanation:</u>

To calculate the moles, we use the following equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

<u>Moles of Lead nitrate:</u>

Given mass of lead nitrate = 8.65 grams

Molar mass of lead nitrate = 331.2 g/mol

Putting values in above equation, we get:

$\text{Number of moles}=\frac{8.65g}{331.2g/mol}=0.0261moles$

<u>Moles of Aluminium:</u>

Given mass of aluminium = 2.5 grams

Molar mass of aluminium = 27 g/mol

Putting values in above equation, we get:

$\text{Number of moles}=\frac{2.5g}{27g/mol}=0.0925moles$

For the given chemical reaction, the equation follows:

$2AI(s)+3Pb(NO_3)_2(aq.)\rightarrow 3Pb(s)+2AI(NO3)_3(aq.$

By Stoichiometry:

3 moles of lead nitrate reacts with 2 moles of aluminium

So, 0.0261 moles of lead nitrate are produced by = $\frac{2}{3}\times 0.0261=0.0174moles$ of aluminium.

As, the required amount of aluminium is less than the given amount. Hence, it is considered as the excess reagent.

Lead nitrate is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

3 moles of lead nitrate are produces 3 moles of lead metal.

So, 0.0261 moles of lead nitrate will produce = $\frac{3}{3}\times 0.0261=0.0261moles$ of lead metal.

Now, to calculate the grams or theoretical yield of lead metal, we put in the mole's equation, we get:

Molar mass of lead = 207.2 g/mol

Putting values in above equation, we get:

$0.0261mol=\frac{\text{Given mass}}{207.2g/mol}$

Mass of lead = 5.408 grams

Hence, the theoretical yield of solid lead comes out to be 5.408 grams.

8 0

3 years ago

When does the given chemical system reach dynamic equilibrium?

AVprozaik [17]

Once it becomes balanced.

7 0

3 years ago