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vaieri [72.5K]
3 years ago
6

Now look closely at the patterns in the table. Compare the elements in each column and row. What can we say about

Chemistry
1 answer:
Finger [1]3 years ago
4 0

Answer: Elements in the same row have the same number of occupied energy levels. For each column, the last occupied energy level has the same number of electrons.

Explanation: Straight from PLATO.

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What is the destiny of an object that has a mass of 20 grams and a volume of 10 millimeters
blondinia [14]

Answer:

2gcm⁻³

Explanation:

Given parameters:

Mass of the object  = 20g

Volume = 10mL

Unknown:

Density of the object  = ?

Solution:

Density of a body is its mass per unit volume;

   Density  = \frac{mass}{volume}  

We need to convert mL to cm³ for the volume

     1mL  = 1cm³;

        10mL is therefore, 10cm³  

So;

       Density  = \frac{20}{10}   = 2gcm⁻³

7 0
3 years ago
What is the concentration of an hbr solution if 12.0 ml of the solution is neutralized by 15.0 ml of a 0.25 m koh solution?
Snowcat [4.5K]
The balanced equation for the reaction between KOH and HBr is as follows;
KOH + HBr --> KBr + H₂O
stoichiometry of KOH to HBr is 1:1
number of KOH moles reacted - 0.25 mol/L x 0.015 L = 0.00375 mol
according to molar ration 
number of KOH moles reacted = number of HBr moles reacted 
number of HBr moles reacted - 0.00375 mol 
if 12 mL of HBr contains - 0.00375 mol 
then 1000 mL of HBr contains - 0.00375 mol / 12 mL x 1000 mL = 0.313 mol
therefore molarity of HBr is 0.313 M
4 0
3 years ago
The aqueous equilibrium reaction below would not be affected by
german

Answer:loko2020 I’m stupid I don’t know no answers sorry

Explanation:xd

5 0
3 years ago
What is the pH at the equivalence point in the titration of a 25.7 mL sample of a 0.370 M aqueous nitrous acid solution with a 0
expeople1 [14]

Answer:

pH = 8.24

Explanation:

Nitrous acid (HNO₂) reacts with KOH, thus:

HNO₂ + KOH → KNO₂ + H₂O

Moles of HNO₂ are:

0.0257mL ₓ (0.370mol / L) = 0.00951moles.

In equivalence point, the complete moles of nitrous acid reacts with KOH producing potassium nitrite. There are needed:

0.00951mol ₓ (1L / 0.491mol) = 0.01937L ≡ 19.4mL of 0.491M KOH to reach equivalence point.

Total volume in equivalence point is: 19.4mL + 25.7mL = <em>45.1mL</em>

Potassium nitrite is in equilibrium with water, thus:

NO₂⁻ + H₂O ⇄ HNO₂ + OH⁻

Where equilibrium constant, Kb, is defined as:

Kb = 1.41x10⁻¹¹ = \frac{[OH^-][HNO_2]}{[NO_2]}

In equilibrium, molarity of each compound are:

[NO₂⁻]: 0.00951mol/0.00451L - X = 0.211M - X

[HNO₂]: X

[OH⁻]: X

<em>Where X is reaction coordinate</em>

Replacing in Kb:

1.41x10⁻¹¹ = \frac{[X][X]}{[0.211 -X]}

0 = X² + 1.41x10⁻¹¹X - 2.97x10⁻¹²

Solving for X:

X = -1.72x10⁻⁶ <em>FALSE ANSWER. There is no negative concentrations.</em>

X = 1.72x10⁻⁶. <em>Right answer.</em>

That means:

[OH⁻]: 1.72x10⁻⁶M

As pOH is -log [OH⁻] and pH = 14-pOH:

pOH = 5.76; <em>pH = 8.24</em>

3 0
3 years ago
The lock-and-key mechanism refers to
miskamm [114]

Answer:

A). The complementary shapes of an enzyme and a substrate.

Explanation:

The Lock-and-key mechanism was proposed by Emil Fischer for the first time and characterized as the metaphor which helps in elucidating the specificity of the enzymatic reactions. In this metaphor, the lock is described as the enzyme while 'key' is characterized as the substrate which the enzyme acts upon. If the key is not appropriately sized, it will not fit into the active site i.e. the keyhole of the lock or enzyme and reaction will not take place. Thus, <u>option A</u> is the correct answer.

5 0
3 years ago
Read 2 more answers
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