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3 years ago

How many moles of NaCl are in 75.0 g of NaCl ?

2 answers:

6 0

Number of moles is found by formula n=mass/molar mass, or m/M. the molar mass is found by adding together the atomic masses of Na and Cl (22.99 + 35.45) to give 58.44 g/mol. Since the mass of NaCl is 75.0g, we find the number of moles as follows:
n = 75.0 / 58.44 = 1.28 mol

Mkey [24]3 years ago

6 0

To find the number of moles of any compound you should divide the mass over the molar mass of that compound

so for your question, 

number of moles = mass/ molar mass 
= 75.0 g / 58.443 g/mol 
= 1.2833 
= 1.28 and note that the answer is rounded to 3 significant figures

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How many electrons are shared in the Lewis structure

Diano4ka-milaya [45]

Hey there,

Answer:

4 valence electrons.

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3 years ago

In acidic aqueous solution, the purple complex ion Co(NH3)5Br2+ undergoes a slow reaction in which the bromide ion is replaced b

kirill115 [55]

Answer:

A) 0.065 M is its molarity after a reaction time of 19.0 hour.

B) In 52 hours $[Co(NH_3)5Br]^{2+}$ will react 69% of its initial concentration.

Explanation:

$Co(NH_3)_5(H_2O)_3+[Co(NH_3)5Br]^{2+}(Purple)(aq)+H_2O(l)\rightarrow [Co(NH_3)_5(H_2O)]^{3+}(Pinkish-orange)(aq)+Br^-(aq)$

The reaction is first order in $[Co(NH_3)5Br]^{2+}$ :

Initial concentration of $[Co(NH_3)5Br]^{2+}$ = $[A_o]=0.100 M$

a) Final concentration of $[Co(NH_3)5Br]^{2+}$ after 19.0 hours= $[A]$

t = 19.0 hour = 19.0 × 3600 seconds ( 1 hour = 3600 seconds)

Rate constant of the reaction = k = $6.3\times 10^{-6} s^{-1}$

The integrated law of first order kinetic is given as:

$[A]=[A_o]\times e^{-kt}$

$[A]=0.100 M\times e^{-6.3\times 10^{-6} s^{-1}\times 19.0\times 3600 s}$

$[A]=0.065 M$

0.065 M is its molarity after a reaction time of 19.0 h.

Initial concentration of $[Co(NH_3)5Br]^{2+}$ = $[A_o]=x$

Final concentration of $[Co(NH_3)5Br]^{2+}$ after t = $[A]=(100\%-69\%) x=31\%x=0.31x$

Rate constant of the reaction = k = $6.3\times 10^{-6} s^{-1}$

The integrated law of first order kinetic is given as:

$[A]=[A_o]\times e^{-kt}$

$0.31x=x\times e^{-6.3\times 10^{-6} s^{-1}\t}$

t = 185,902.06 s = $\frac{185,902.06 }{3600} hour = 51.64 hours$ ≈ 52 hours

In 52 hours $[Co(NH_3)5Br]^{2+}$ will react 69% of its initial concentration.

6 0

4 years ago

According to the Law of Conservation of Mass, how much water is produced if 22.5 g of

nadezda [96]

Answer: The amount of water produced is 9.3 grams

Explanation:

According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

$CH_4+2O_2\rightarrow CO_2+2H_2O$

mass of reactants = mass of methane + mass of oxygen = 22.5 g + 35.7 g = 58.2 g

mass of products = mass of carbon dioxide + mass of water = 48.9 g + mass of water

48.9 g + mass of water = 58.2 g

mass of water = 9.3 g

4 0

3 years ago

A buffered solution has a pH of 7.5. What would happen to the pH if a small

musickatia [10]

Answer:

Dear user,

Answer to your query is provided below

When small amount of acid was added to buffered solution, pH will change very less.

Explanation:

Buffer solution resists change in ph on adding small amount of acid or base but when we calculate the value of buffer capacity we take the change in ph when we add acid or base to 1 lit solution of buffer.This contradicts the definition of buffer solution.

5 0

3 years ago

How many grams of butane can be burned by 1.42 moles of oxygen?

Mrrafil [7]

Answer:

So the molar mass of C4,H10 is

58.12g mole -1

6 0

3 years ago