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padilas [110]
3 years ago
11

What was discovered first helium or samarium?

Chemistry
1 answer:
lana [24]3 years ago
7 0
The correct answer is helium, but both discoveries were quite close. Helium was discovered in 1868 during a solar eclipse by French astronomer Jules Janssen, while samarium was discovered in 1879 by a French chemist Paul Émile Lecoq de Boisbaudran.
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pav-90 [236]

Answer:

4

Explanation:

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3 years ago
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Atoms join together to form compounds by gaining losing or sharing
Y_Kistochka [10]
It is sharing (i could be wrong so be cautious of your answer) <span />
8 0
3 years ago
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Farmers who raise cotton once used arsenic acid, H3AsO4, as a defoliant at harvest time. Arsenic acid is a polyprotic acid with
Bess [88]

Answer:

pH = 1.95

Explanation:

For polyprotic acids, it is generally assumed that all H⁺ comes from the 1st ionization step. The amount of H⁺ delivered into solution for the 2nd and 3rd ionization steps are in the order of 10⁻⁴M and 10⁻⁶M respectively and provide very little change in pH from the quantity delivered in the 1st ionization step.

Therefore... the [H⁺] concentraion and pH are computed as follows...

[H⁺] = √Ka₁[H₃AsO₄] = √(2.5 x 10⁻⁴)(0.500) M = 0.1118M

pH = -log[H⁺] = -log(0.01118) = 1.95

8 0
3 years ago
The atomic mass and abundance of Cr-50 is 49.946 amu and 4.3%. The atomic mass and abundance of Cr-52 is 51.941 amu and 83.8%. T
Leviafan [203]

Answer:

52.00 AMU

Explanation:

(49.946 * 0.043) + (51.941 * 0.838) + (52.941 * 0.095) + (53.939 * 0.024) = 51.998

Make sure to round, 52.00 AMU.

3 0
3 years ago
In the laboratory, hydrogen gas is usually made by the following reaction: Zn(s) + 2 HCl(aq) → H2(g) + ZnCl2(aq) How many liters
IrinaK [193]

<u>Answer:</u> The volume of hydrogen gas collected over water is 2.13 L

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

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

Given mass of zinc = 5.566 g

Molar mass of zinc = 65.4 g/mol

Putting values in above equation, we get:

\text{Moles of zinc}=\frac{5.566g}{65.4g/mol}=0.0851mol

For the given chemical reaction:

Zn(s)+2HCl(aq.)\rightarrow H_2(g)+ZnCl_2(aq.)

As, HCl is present in excess. So, it is considered as an excess reagent.

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

By Stoichiometry of the reaction:

1 mole of zinc produces 1 mole of hydrogen gas.

So, 0.0851 moles of zinc will produce = \frac{1}[1}\times 0.0851=0.0851mol of hydrogen gas

To calculate the volume of hydrogen gas, we use ideal gas equation, which is:

PV = nRT

where,

P = Pressure of hydrogen gas = Total atmospheric pressure - vapor pressure of water = (752 - 18.65) mmHg = 733.35 mmHg

V = Volume of the hydrogen gas

n = number of moles of gas = 0.0851 moles

R = Gas constant = 62.3637\text{ L.mmHg }mol^{-1}K^{-1}

T = Temperature of hydrogen gas = 21^oC=[21+273]K=294K

Putting values in above equation, we get:

733.35mmHg\times V=0.0851mol\times 62.3637\text{ L.mmHg }mol^{-1}K^{-1}\times 294K\\\\V=\frac{0.0851\times 62.3637\times 294}{733.35}=2.13L

Hence, the volume of hydrogen gas collected over water is 2.13 L

5 0
3 years ago
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