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Mandarinka [93]
3 years ago
5

Metals and nonmetals all lesson explanation for class 8​

Chemistry
1 answer:
WINSTONCH [101]3 years ago
7 0

Answer:

Metalloids elements whose properties are intermediate between those of metals and solid nonmetals or semiconductors.

Some examples:

Chemical element.

Boron.

Semiconductor.

Arsenic.

Silicon.

Selenium.

Antimony.

Germanium.

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Codeine C18H21NO3 is a weak organic base. A 5.0 x 10^-3 M solution of codeine has a pH of 9.95. Calculate the value of Kb for th
arsen [322]

Answer:

Kb = 4.45\times10^{-7}\ mol/L

p^{Kb}=6.35

Explanation:

For a weak organic base, the formula to find p^{OH} is given by:

p^{OH}=p^{K_b}+\log c

where c is the concentration of base.

Here c= 5\times10^{-3}\ M

p^{H}=9.95\\p^{OH}=14-p^{H}=14-9.95=4.05

Substituting the above values in the formula,we get:

p^{k_b}=p^{OH}-\log c\\p^{k_b}=4.05-\log (5\times10^{-3})\\p^{K_b}=6.35\\K_b=$antilog 6.35=4.45\times10^{-7}\ mol/L

Hence:

Kb = 4.45\times10^{-7}\ mol/L

p^{Kb}=6.35

7 0
2 years ago
For the gas phase decomposition of t-butyl propionate,C2H5COOC(CH3)3 (CH3)2C=CH2 + C2H5COOHthe rate constant at 540 K is 8.90×10
kvv77 [185]

Answer:

The activation energy is 164.02 kJ/mol

Explanation:

Log (k2/k1) = Ea/2.303R × [1/T1 - 1/T2]

k1 = 8.9×10^-4 s^-1

k2 = 9.83×10^-3 s^-1

R = 8.314 J/mol.K

T1 = 540 K

T2 = 578 K

Log (9.83×10^-3/8.9×10^-4) = Ea/2.303×8.314 × [1/540 - 1/578]

1.043 = 6.359×10^-6Ea

Ea = 1.043/6.359×10^-6 = 164020 J/mol = 164020/1000 = 164.02 kJ/mol

6 0
3 years ago
Sodium azide decomposes rapidly to produce nitrogen gas.
brilliants [131]

Answer:

156 g

Explanation:

Let's consider the following reaction.

2 NaN₃(s) → 2 Na(s) + 3 N₂ (g)

We can find the moles of N₂  using the ideal gas equation.

P × V = n × R × T

1.50 atm × 60.0 L = n × (0.08206 atm.L/mol.K) × 305 K

n = 3.60 mol

The molar ratio of N₂ to NaN₃ is 3:2. The moles of NaN₃ are:

3.60 mol N₂ × (2 mol NaN₃ / 3 mol N₂) = 2.40 mol NaN₃

The molar mass of NaN₃ is 65.01 g/mol. The mass of NaN₃ is:

2.40 mol × 65.01 g/mol = 156 g

4 0
3 years ago
. What is the molarity of a solution that was prepared by dissolving 80.0 g of CaCl2 (molar mass = 111.1 g/mol) in enough water
garri49 [273]

Explanation:

Molarity = mol/L or g/L

Data:

Mass>80.0g

Mr of CaCl2>111.1g/mol

V>500mL

Convert mL to Litres;. mole=g/Mr

1L=1000mL. =80g/111.1g/mol

x=500mL. =0.720072007mol

x=0.5L

Molarity= mole/volume

=0.720072007mol/0.5L

=1.440144014mol/L

=1.4401mol/L

Hope this helps. Depending on the question you can also find it in g/L but mol/L is safer.

7 0
2 years ago
Which of the following could have caused curve B to be different from curve A?
Mamont248 [21]

A. More reactants could have been added to reaction B










6 0
3 years ago
Read 2 more answers
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