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4 years ago

What is chemistry? please tell me

1 answer:

8 0

Chemistry is the scientific discipline involved with elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.

You might be interested in

Explain why a steel object continues to rust even after its outer layers have corroded.

Aliun [14]

Answer:

Explanation:

During that process of being exposed to air and water while being left outside or in the elements for an extended period of time, a variety of different types of rusts can form, but the most common form is Fe2O3. Rust only forms on the outside of a metal surface because it requires exposure of oxygen and water to rust.

7 0

3 years ago

How many moles are in 3.4 x 10-7 grams of Silicon dioxide, SiO2?

Varvara68 [4.7K]

Answer:

Number of moles = 0.057 × 10⁻⁷ mol

Explanation:

Given data:

Mass of SiO₂ = 3.4 × 10⁻⁷ g

Number of moles = ?

Solution:

Number of moles = mass/molar mass

Molar mass of SiO₂ = 60 g/mol

by putting values,

Number of moles = 3.4 × 10⁻⁷ g / 60 g/mol

Number of moles = 0.057 × 10⁻⁷ mol

8 0

3 years ago

How do I answer and do this

Alecsey [184]

a) When the reaction takes place a yellow precipitate will be formed.

b) The law of conservation of mass is true.

Explanation:

a) When a lead nitrate solution is mixed with a potassium chromate solution, a yellow precipitate containing lead forms according to the equation:

$Pb(NO_3)_2 (aq) + K_2CrO_4 (aq)$ → $2 KNO_3 (aq) + PbCrO_4(s).$

b) Law of conservation of mass for the given reaction is true.

From the given table we know the mass of reactants and its products.

Law of conservation of mass is a principle when a reaction takes place in a closed system, the mass of the products and reactants in the system doesn't change.

⇒The sum of the mass of the reactants = The sum of the mass of the products.

The sum of the reactants = 128.71+128.97.

= 257.68 g.

The sum of the products = 154.10+103.58.

= 257.68 g.

Thus law of conservation of mass is true for the above reaction.

3 0

3 years ago

How many kilojoules are released when 8.2 g of water condenses at 100 °c and cools to 15 °c?

MrRa [10]

Answer:- 2.92 kJ of heat is released.

Solution:- We have water at 100 degree C and it's going to be cool to 15 degree C.

So, change in temperature, $\Delta T$ = 15 - 100 = -85 degree C

mass of water, m = 8.2 g

specific heat of water, c = $4.184\frac{J}{^0C.g}$

The equation used for solving this type of problems is:

$q=mc\Delta T$

Let's plug in the values in the equation and solve it for q which is the heat energy:

q = (8.2)(4.184)(-85)

q = -2916.248 J

They want answer in kJ. So, let's convert J to kJ and for this we divide by 1000.

$q=-2916.248J(\frac{1kJ}{1000J})$

q = -2.92 kJ

Negative sign indicates the heat is released. So, in the above process of coiling of water, 2.92 kJ of heat is released.

3 0

4 years ago

The balanced equation for a hypothetical reaction is a + 5b + 6c → 3d + 3e. what is the rate law for this reaction? rate = k [a]

nekit [7.7K]

Answer: The correct rate of the reaction is $Rate=k[a][b]^5[c]^6$

Explanation:

Rate law of the reaction is the expression which expresses the rate of the reaction in the terms of the molar concentrations of the reactants with each term raised to the power of their respective stoichiometric coefficients in a balanced chemical equation.

For the given reaction:

$a+5b+6c\rightarrow 3d+3e$

The expression for the rate law will be: $Rate=k[a][b]^5[c]^6$

7 0

3 years ago