A student dissolved 5.00 g of Co(NO3)2 in enough water to make 100. mL of stock solution. He took 4.00 mL of the stock solution and then diluted it with water to give 275. mL of a final solution. How many grams of NO3- ion are there in the final solution?

$Co(NO_3)_2(aq)\rightarrow Co^{2+}(aq)+2NO_3^{-}(aq)$

Initial mole of Co(NO3)2 $=\frac{mass}{molar mass}$

$=\frac{5.00}{182.94} \\\\=0.02733mol$

Mole of Co(NO3)2 in final solution

$=\frac{4.00}{100}\times 0.02733\\\\=0.04\times 0.02733\\\\= 0.001093mol$

Mole of NO3- in final solution = 2 x Mole of Co(NO3)2

$=2\times 0.001093\\\\=0.002186mol$

Mass of NO3- in final solution is mole x Molar mass of NO3

$=0.002186\times62.01\\\\=0.136g$

6 0

4 years ago

What is the number of valence electrons that most atoms prefer?

Nataly_w [17]

Answer: 8 electrons

Explanation: Valence electrons are the electrons in the outermost shell of an atom and they are important in chemical reactions.

Atoms are <em>happy</em> when they follow the octet rule which states that 2 electrons can go in the first shell and 8 electrons can go in the other shells.

Electrons are happy when they have a full outer shell which usually needs to be 8 electrons. However, some of the smaller elements like helium are happy because they can hold a max of 2 electrons and helium has 2 electrons since it has 2 protons in its core as well as 2 electrons in its energy levels.

4 0

3 years ago

Read 2 more answers

A substance added in The final stages to remove sulphur from coal is

Deffense [45]

Answer:

calcium oxide is injected into the final stage of the scubber, wich then reacts with the sulfur dioxide to form calcium sulfite.

Explanation:

8 0

3 years ago