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3 years ago

What are two examples of a chemical change

Chemistry

2 answers:

lyudmila [28]3 years ago

6 0

Answer:

1.Cooking an egg

2. Burning wood

Hope it helps :)

Taya2010 [7]3 years ago

5 0

Answer:

1.Mixing of sodium with water

2.rusting of iron

Step by step explanation:

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Which list of elements consists of a metal, a metalloid, and a nonmetal?

Irina18 [472]

Answer:

Sn, Si, C

Explanation:

8 0

3 years ago

"How much NH4Cl, when present in 2.00 liters of 0.200 M ammonia, will give a solution with pH = 8.20? For NH3, Kb = 1.8 x 10-5"

Andru [333]

Answer:

245.66g of NH₄Cl is the mass we need to add to obtain the desire pH

Explanation:

The mixture of NH3/NH4Cl produce a buffer. We can find the pH of a buffer using H-H equation:

pH = pKa + log [A⁻] / [HA]

Where [A⁻] is the molar concentration of the base, NH₃, and [HA] molar concentration of the acid, NH₄⁺. This molar concentration can be taken as the moles of each chemical

First, we need to find pKa of NH₃ using Kb. Then, the moles of NH₃ and finally replace these values in H-H equation to solve moles of NH₄Cl we need to obtain the desire pH.

pKa NH₃/NH₄⁺

pKb = - log Kb

pKb = -log 1.8x10⁻⁵ = 4.74

pKa = 14 - pKb

pKa = 14 - 4.74

pKa = 9.26

Moles NH₃

2.00L ₓ (0.200mol NH₃ / L) = 0.400 moles NH₃

H-H equation:

pH = pKa + log [NH₃] / [NH₄Cl]

8.20 = 9.26 + log [0.400 moles] / [NH₄Cl]

-1.06 = log [0.400 moles] / [NH₄Cl]

0.0087 = [0.400 moles] / [NH₄Cl]

[NH₄Cl] = 0.400 moles / 0.0087

[NH₄Cl] = 4.59 moles of NH₄Cl we need to add to original solution to obtain a pH of 8.20. In grams (Using molar mass NH₄Cl=53.491g/mol):

4.59 moles NH₄Cl ₓ (53.491g / mol) =

<h3>245.66g of NH₄Cl is the mass we need to add to obtain the desire pH</h3>

3 0

3 years ago

What is the molar concentration of 35 mL of H2SO4 that neutralizes 25 mL of 0.320M NaOH

stira [4]

V ( H2SO4) = 35 mL / 1000 => 0.035 L

M ( H2SO4) = ?

V ( NaOH ) = 25 mL / 1000 => 0.025 L

M ( NaOH ) = 0.320 M

number of moles NaOH:

n = M x V

n = 0.025 x 0.320 => 0.008 moles of NaOH

Mole ratio:

2 NaOH + H2SO4 = Na2SO4 + 2 H2O

2 moles NaOH ---------------------- 1 mole H2SO4
0.008 moles moles NaOH ---------- ??

0.008 x 1 / 2 => 0.004 moles of H2SO4 :

Therefore:

M ( H2SO4) = n / V

M = 0.004 / 0.035

= 0.114 M

hope this helps!

6 0

3 years ago

Differentiate between elements and mixtures

Ksenya-84 [330]

Answer:

ELEMENTS MIXTURE

Elements are made up of one kind of atoms. Mixtures are made up of two or more kinds of Compounds .

Elements cannot be broken down into simpler substances by any physical or chemical method. The various constituents are seperated by simple physical means

3 0

2 years ago

Read 2 more answers

Problem page in each of the molecules drawn below one chemical bond is colored red. decide whether this bond is likely to be pol

Slav-nsk [51]

The question is incomplete, here is the complete question:

Problem page in each of the molecules drawn below one chemical bond is colored red. Decide whether this bond is likely to be polar or not. if the bond is likely to be polar, write down the chemical symbol for the atom which will have more negative charge.

The image is attached below.

Answer:

For carbon dioxide molecule: The bond is considered as polar and the elecvtronegative atom is oxygen.

For water molecule: The bond is considered as polar and the elecvtronegative atom is oxygen.

Explanation:

There are two types of covalent bonds:

Polar covalent bond: This bond is formed when difference in electronegativity between the atoms is present. When atoms of different elements combine, it results in the formation of polar covalent bond. For Example: $CO_2,NO_2$ etc..
Non-polar covalent bond: This bond is formed when there is no difference in electronegativity between the atoms. When atoms of the same element combine, it results in the formation of non-polar covalent bond. For Example: $N_2,O_2$ etc..

In carbon dioxide molecule:

The given bond is present between C and O atom.

Electronegativity value of C = 2.5

Electronegativity value of O = 3.5

Electronegativity difference = (3.5 - 2.5) = 1

As, electronegativity difference is present. So, the bond is considered as polar and the elecvtronegative atom is oxygen.

In water molecule:

The given bond is present between H and O atom.

Electronegativity value of H = 2.1

Electronegativity value of O = 3.5

Electronegativity difference = (3.5 - 2.1) = 1.4

As, electronegativity difference is present. So, the bond is considered as polar and the elecvtronegative atom is oxygen.

8 0

3 years ago