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4 years ago

Why do scientist use models to study atoms and molecules?

1 answer:

6 0

This allows us to visually see the structure of the atoms/ molecules so we can get a better understanding of what they look like.

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Predict whether the following reactions will be exothermic or endothermic. Reaction A. N 2 ( g ) + 3 H 2 ( g ) ⟶ 2 NH 3 ( g ) Re

Marina86 [1]

Answer :

Exothermic reactions : A, B, D

Endothermic reaction : C

Explanation :

Endothermic reaction : It is defined as the chemical reaction in which the energy is absorbed from the surrounding.

In the endothermic reaction, the energy of reactant are less than the energy of product.

Exothermic reaction : It is defined as the chemical reaction in which the energy is released into the surrounding.

In the exothermic reaction, the energy of reactant are more than the energy of product.

As we know that, heat is released in the bond formation and heat is required in the bond breaking.

Reaction (A):

$N_2(g)+3H_2(g)\rightarrow 2NH_3(g)$

In this reaction, the more bonds are formed than the bond broken. That means, heat will be released. So, It is an exothermic reaction.

Reaction (B):

$S(g)+O_2(g)\rightarrow SO_2(g)$

In this reaction, burning of sulfur with oxygen takes place. That means, heat will be released. So, It is an exothermic reaction.

Reaction (C):

$2H_2O(g)\rightarrow 2H_2(g)+O_2(g)$

This reaction is a decomposition reaction. That means, heat will be required. So, It is an endothermic reaction.

Reaction (D):

$2F(g)\rightarrow F_2(g)$

In this reaction, formation of fluorine molecule from its atoms releases heat. So, It is an exothermic reaction.

Hence, the exothermic reactions are, A, B, D and endothermic reaction is, C

3 0

3 years ago

How many grams of NaCl should be added to 250 grams of waterto<br> make a 0.40 m solution?

brilliants [131]

Answer:

5.85 grams of NaCl should be added to 250 grams of water to make a 0.40 m solution.

Explanation:

$molality=\frac{\text{Mass of solute}}{\text{Molar mass of solute}\times \text{ Mass of solvent (kg)}}$

Mass of NaCl =x

Molar mass of NaCl = 58.5 g/mol

Molality of the solution = 0.40 m

Mass of the solvent = 250 g = 0.250 kg (1g = 0.001 kg)

$0.40 m=\frac{x}{58.5 g/mol\times 0.250 kg}$

$x=0.40 m\times 58.5 g/mol\times 0.250 kg=5.85 g$

5.85 grams of NaCl should be added to 250 grams of water to make a 0.40 m solution.

7 0

3 years ago

What volume of so2 is produced at 325 k and 1.35 atm when 15.0 grams of hcl reacts with excess k2so3?

Helen [10]

The balanced equation for the above reaction is as follows;
2HCl + K₂SO₃ ---> 2KCl + H₂O + SO₂
stoichiometry of HCl to SO₂ is 2:1
number of moles of HCl reacted - 15.0 g / 36.5 g/mol = 0.411 mol
according to molar ratio
number of SO₂ moles formed - 0.411 mol /2 = 0.206 mol
since we know the number of moles we can find volume using ideal gas law equation
PV = nRT
where
P - pressure - 1.35 atm x 101 325 Pa/atm = 136 789 Pa
V - volume
n - number of moles - 0.206 mol
R - universal gas constant - 8.314 Jmol⁻¹K⁻¹
T - temperature - 325 K
substituting values in the equation

136 789 Pa x V = 0.206 mol x 8.314 Jmol⁻¹K⁻¹ x 325 K
V = 4.07 L
volume of SO₂ formed is 4.07 L

8 0

4 years ago

Define Conversion Factor in CHEMISTRY? Define Conversion Factor in CHEMISTRY

Artemon [7]

A conversion factor is a ratio (or fraction) which represents the relationship between two different units :)

8 0

3 years ago

The decomposition of nitramide in aqueous solution at 25 °C NH2NO2(aq)N2O(g) + H2O(l) is first order in NH2NO2 with a rate const

HACTEHA [7]

Answer:

$[NH_2NO_2]=0.0868M$