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Ulleksa [173]
3 years ago
8

What is the mass number of 207Pb ? A: 289 B: 207 C: 125 D: 82

Chemistry
1 answer:
Sergio [31]3 years ago
3 0
207 is the mass number. 82 would be the atomic number
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Aluminum metal reacts with aqueous cobalt(II) nitrate to form aqueous aluminum nitrate and cobalt metal. What is the stoichiomet
Lelu [443]

Answer:

the stoichiometric coefficient for cobalt is 3

Explanation:

the unbalanced reaction would be

Co(NO₃)₂+ Al → Al(NO₃)₃ + Co

One way to solve is to build a system of linear equations for each element (or group as NO₃) , knowing that the number of atoms of each element is conserved.

For smaller reactions a quick way to solve it can be:

- First the Co as product and as reactant needs to have the same stoichiometric coefficient

- Then the Al as product and as reactant needs to have the same stoichiometric coefficient

- After that we look at the nitrates . There are 2 as reactants and 3 as products . Since the common multiple is 6 then multiply the reactant by 3 and the product by 2.

Finally the balanced equation will be

3 Co(NO₃)₂+ 2 Al → 2 Al(NO₃)₃ + 3 Co

then the stoichiometric coefficient for cobalt is 3

7 0
3 years ago
1) What happened at Chernobyl in 1986? How many people died?
ch4aika [34]

Answer: According to the BBC, the internationally recognized death toll shows that 31 died as an immediate result of Chernobyl. Two workers died at the site of the explosion, another died in hospital soon after due to their injuries and 28 operators and firemen are believed to have died within three months of the accident.

Explanation:

6 0
2 years ago
Which statement best describes the oxidation numbers of the atoms found in magnesium chloride? A. Magnesium has a 2- oxidation n
In-s [12.5K]
B. is the correct answer of your question
6 0
3 years ago
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How many moles of H 2 can be formed if a 3.24 g sample of M g reacts with excess H C l ?
Ganezh [65]

Answer:

0.135 mole of H2.

Explanation:

We'll begin by calculating the number of mole in 3.24 g of Mg. This can be obtained as follow:

Mass of Mg = 3.24 g

Molar mass of Mg = 24 g/mol

Mole of Mg =?

Mole = mass /Molar mass

Mole of Mg = 3.24/24

Mole of Mg = 0.135 mole

Next, we shall write the balanced equation for the reaction. This is illustrated below:

Mg + 2HCl —> MgCl2 + H2

From the balanced equation above,

1 mole of Mg reacted to produce 1 mole of H2.

Finally, we shall determine the number of mole of H2 produced by reacting 3.24 g (i.e 0.135 mole) of Mg. This can be obtained as follow:

From the balanced equation above,

1 mole of Mg reacted to produce 1 mole of H2.

Therefore, 0.135 mole of Mg will also react to produce 0.135 mole of H2.

Thus, 0.135 mole of H2 can be obtained from the reaction.

3 0
3 years ago
The element with the most stable nucleus and smallest mass per particle is
Margaret [11]
"18) the element with the most stable nucleus and smallest mass per particle is:A) uranium.B)argon C) helium."
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