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3 years ago

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Convert 78.9 kJ into calories (can you also explain how pls, ty <3)

1 answer:

Elza [17]3 years ago

3 0

Answer:

1 Joule=0.2390057361 Calorie

789kj=789×0.2390057361×1000

=188575.5257829calorie

Explanation:

Hope u have understand

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True or false. An excited state is less stable than a ground state

vladimir2022 [97]

Answer: True!

Explanation: As electrons that are excited move between energy levels, they emit lots and lots of energy, in fact way more energy than ground state electrons (electrons that move within the same energy level) do, thus, making them more unstable.

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3 years ago

Solid NaI is slowly added to a solution that is 0.0079 M Cu+ and 0.0087 M Ag+.Which compound will begin to precipitate first?NaI

NeTakaya

Answer :

AgI should precipitate first.

The concentration of $Ag^+$ when CuI just begins to precipitate is, $6.64\times 10^{-7}M$

Percent of $Ag^+$ remains is, 0.0076 %

Explanation :

$K_{sp}$ for CuI is $1\times 10^{-12}$

$K_{sp}$ for AgI is $8.3\times 10^{-17}$

As we know that these two salts would both dissociate in the same way. So, we can say that as the Ksp value of AgI has a smaller than CuI then AgI should precipitate first.

Now we have to calculate the concentration of iodide ion.

The solubility equilibrium reaction will be:

$CuI\rightleftharpoons Cu^++I^-$

The expression for solubility constant for this reaction will be,

$K_{sp}=[Cu^+][I^-]$

$1\times 10^{-12}=0.0079\times [I^-]$

$[I^-]=1.25\times 10^{-10}M$

Now we have to calculate the concentration of silver ion.

The solubility equilibrium reaction will be:

$AgI\rightleftharpoons Ag^++I^-$

The expression for solubility constant for this reaction will be,

$K_{sp}=[Ag^+][I^-]$

$8.3\times 10^{-17}=[Ag^+]\times 1.25\times 10^{-10}M$

$[Ag^+]=6.64\times 10^{-7}M$

Now we have to calculate the percent of $Ag^+$ remains in solution at this point.

Percent of $Ag^+$ remains = $\frac{6.64\times 10^{-7}}{0.0087}\times 100$

Percent of $Ag^+$ remains = 0.0076 %

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3 years ago

How many milliliters of ammonium sulfate solution having a concentration of 0.218 M are needed to react completely with 62.6 ml

BartSMP [9]

Answer:

330 mL of (NH₄)₂SO₄ are needed

Explanation:

First of all, we determine the reaction:

(NH₄)₂SO₄ + 2NaOH → 2NH₃ + 2H₂O + Na₂SO₄

We determine the moles of base:

(First, we convert the volume from mL to L) → 62.6 mL . 1L/1000 mL = 0.0626L

Molarity . volume (L) = 2.31 mol/L . 0.0626 L = 0.144 moles

Ratio is 2:1. Therefore we make a rule of three:

2 moles of hydroxide react with 1 mol of sulfate

Then, 0.144 moles of NaOH must react with (0.144 .1) /2 = 0.072 moles

If we want to determine the volume → Moles / Molarity

0.072 mol / 0.218 mol/L = 0.330 L

We convert from L to mL → 0.330L . 1000 mL/1L = 330 mL

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How can a flame test identify an unknown element?

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the answer for this question is the option D

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How many valence electrons configuration of oxygen?

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Oxygen had 6 valence electrons

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3 years ago