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3 years ago

1. What are the rows of the periodic table called and what do they tell us?

Chemistry

1 answer:

Vedmedyk [2.9K]3 years ago

7 0

Answer:

The elements are arranged in seven horizontal rows, called periods or series, and 18 vertical columns, called groups.

Each row represents one period; the period number of an element indicates how many of its energy levels house electrons. Sodium, for instance, sits in the third period, which means a sodium atom typically has electrons in the first three energy levels.

Explanation:

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Buffering capacity refers to: the effectiveness of commercial antacids the extent to which a buffer solution can counteract the

kirill [66]

Answer: Option (b) is the correct answer.

Explanation:

Buffere is defined as the solution to whom when an acid or base is added then it resists any in change in pH of the solution.

This is because a buffer has the ability to not get affected by the addition of small amounts of an acid or a base. So, basically it keeps the concentration of both hydrogen ions and hydroxides equal. As a result, it helps in maintaining the pH of the solution.

And, the capacity of a buffer solution to resist the change is known as buffer capacity.

Thus, we can conclude that buffering capacity refers to the extent to which a buffer solution can counteract the effect of added acid or base.

8 0

3 years ago

Calculate the standard entropy of vaporization of ethanol at its boiling point, 352 K. The standard molar enthalpy of vaporizati

Korvikt [17]

Answer : The correct option is, (b) +115 J/mol.K

Explanation :

Formula used :

$\Delta S=\frac{\Delta H_{vap}}{T_b}$

where,

$\Delta S$ = change in entropy

$\Delta H_{vap}$ = change in enthalpy of vaporization = 40.5 kJ/mol

$T_b$ = boiling point temperature = 352 K

Now put all the given values in the above formula, we get:

$\Delta S=\frac{\Delta H_{vap}}{T_b}$

$\Delta S=\frac{40.5kJ/mol}{352K}$

$\Delta S=115J/mol.K$

Therefore, the standard entropy of vaporization of ethanol at its boiling point is +115 J/mol.K

8 0

4 years ago

What is the percentage composition for H2O in this compound Al(OH)3.2H2O?

Gelneren [198K]

Answer:

32.73%

Explanation:

To solve this problem, first find the molar mass of Al(OH)₃.2H₂O

Atomic mass of Al = 27g/mol

O = 16g/mol

H = 1g/mol

Molar mass = 27 + 3(16 + 1) + 2(2(1) + 16)

= 27 + 51 + 36

= 114g/mol

Percentage composition = $\frac{36}{114}$ x 100 = 32.73%

6 0

3 years ago

In the laboratory a student determines the specific heat of a metal. He heats 19.5 grams of copper to 98.27 °C and then drops it

siniylev [52]

Answer:

The specific heat of copper is 0.37 J/g°C

Explanation:

Step 1: Data given

Mass of copper = 19.5 grams

Initial temperature of copper = 98.27 °C

Mass of water = 76.3 grams

Initial temperature of water = 24.05 °C

Final temperature of water and copper = 25.69 °C

Step 2: Calculate specific heat of copper

Qgained = -Qlost

Q = m*c*ΔT

Qwater = -Qcopper

m(water) * c(water) * ΔT(water) = - m(copper) * c(copper) *ΔT(copper)

⇒ with m(water) = 76.3 grams

⇒ with c(water) = 4.184 J/g°C

⇒ with ΔT(water) = T2-T1 = 25.69 - 24.05 = 1.64

⇒ with m(copper) = 19.5 grams

⇒ with c(copper) = TO BE DETERMINED

⇒ with ΔT(copper) = T2-T1 = 25.69 - 98.27 = -72.58

76.3 * 4.184 * 1.64 = - 19.5 * c(copper) * -72.58

523.552 = 1415.31 * c(copper)

c(copper) = 0.37 J/g°C

The specific heat of copper is 0.37 J/g°C

3 0

4 years ago

You have 15.0 L of nitrogen gas at 100°C and 200 kPa. What volume of gas will you have at STP?

Pavel [41]

Actually, you do NOT need to calculate the number of moles, so you do NOT need to convert the volume and pressure. (You DO have to convert the temperature.) That's because for this problem, pV/T is constant, so the units cancel (but the temperature scale matters).

200kPa * 15L / 373K = 101kPa * V / 273K 
V = 21.7 L

7 0

4 years ago