1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Zarrin [17]
3 years ago
12

A chemist must prepare of potassium hydroxide solution with a pH of at . He will do this in three steps: Fill a volumetric flask

about halfway with distilled water. Weigh out a small amount of solid potassium hydroxide and add it to the flask. Fill the flask to the mark with distilled water. Calculate the mass of potassium hydroxide that the chemist must weigh out in the second step. Round your answer to significant digits
Chemistry
1 answer:
maksim [4K]3 years ago
3 0

The question is incomplete; the complete question is:

A chemist must prepare 800.0mL of potassium hydroxide solution with a pH of 13.00 at 25 degree C. He will do this in three steps: Fill a 800.0mL volumetric flask about halfway with distilled water. Weigh out a small amount of solid potassium hydroxide and add it to the flask. Fill the flask to the mark with distilled water. Calculate the mass of potassium hydroxide that the chemist must weigh out in the second step. Round your answer to 2 significant digits.

Answer:

4.5g (to 2 significant digits)

Explanation:

Now we must remember that KOH is a strong base, therefore it will practically dissociate completely.

To find the pH we can use the equation pH + pOH = 14.

Firstly to find the pOH:

13.00 + pOH = 14

pOH = 1.00

To find the [OH-]

Since

pOH= -log[OH^-]

[OH^-] = antilog (-pOH)

[OH^-]= antilog (-1)

[OH^-] = 0.1 molL-1

Since we've established that KOH is a strong base, we know that [OH-] = [KOH]

Also, we know that concentration = number of moles/volume

we have the concentration and the volume now so we can calculate the number of number of moles as follows:

The 800mL volume is the same as 0.8L

0.1 molL-1= number of moles/0.8L

0.08 moles = number of moles

now we can calculate the amount of solid KOH required

the molar mass of KOH = 39 + 16 +1 = 56 gmol-1

56 x 0.08 moles = 4.48g

So in 800mL of pH 13.00 KOH there is 4.5g of KOH dissolved.

You might be interested in
Nai(aq)+hg2(no3)2(aq)→ express your answer as a chemical equation. identify all of the phases in your answer. enter noreaction i
Komok [63]
<span>Balanced chemial equation:

2NaI(aq)+Hg2(NO3)2(aq) →Hg2 I2 (s) + 2 NaNO3 (aq)

You can see it better if I use latex:

2NaI(aq)+Hg_2(NO_3)_2(aq) =Hg_2 I_2 (s) + 2 NaNO_3 (aq)

As per the phases this is the interpretation:

The symbols (aq) stands for aquous meaning that the compound is dissolved in water.

The symbol (s) stands for solid, meaning tha the compound precipitate and is not dissolved in water.</span><span>


</span>
7 0
4 years ago
A sample of ammonia ^NH3h gas is completely decomposed to nitrogen and hydrogen gases over heated iron wool. If the total pressu
icang [17]

Answer : The partial pressure of N_2 and H_2 is, 216.5 mmHg and 649.5 mmHg

Explanation :

According to the Dalton's Law, the partial pressure exerted by component 'i' in a gas mixture is equal to the product of the mole fraction of the component and the total pressure.

Formula used :

p_i=X_i\times p_T

X_i=\frac{n_i}{n_T}

So,

p_i=\frac{n_i}{n_T}\times p_T

where,

p_i = partial pressure of gas

X_i = mole fraction of gas

p_T = total pressure of gas

n_i = moles of gas

n_T = total moles of gas

The balanced decomposition of ammonia reaction will be:

2NH_3\rightarrow N_2+3H_2

Now we have to determine the partial pressure of N_2 and H_2

p_{N_2}=\frac{n_{N_2}}{n_T}\times p_T

Given:

n_{N_2}=1\\\\n_{H_2}=3\\\\n_{T}=4\\\\p_T=866mmHg

p_{N_2}=\frac{1}{4}\times (866mmHg)=216.5mmHg

and,

p_{H_2}=\frac{n_{H_2}}{n_T}\times p_T

Given:

n_{H_2}=1\\\\n_{H_2}=3\\\\n_{T}=4\\\\p_T=866mmHg

p_{H_2}=\frac{3}{4}\times (866mmHg)=649.5mmHg

Thus, the partial pressure of N_2 and H_2 is, 216.5 mmHg and 649.5 mmHg

5 0
3 years ago
Solution A has twice as much solute as solution B is it possible for the solutions to have the same concentration
pishuonlain [190]
Yes. As long as the ratio of solute and solvent is same for both solution, the solution has the same concentration. for example, solution A has 2 ml of water, and 1 ml of sucrose. Solution B has 4ml of water and 2ml of sucrose. Both has a ratio of water to sucrose by 2 : 1. they have the same concentration of 50% sucrose. 
5 0
4 years ago
Hi! ❤️ , im looking for some help here. ill give brainliest if able to.
dexar [7]

A student builds a model of a race car. The scale is 1:15. In the scale model, the car is 8 cm tall. How tall is the actual car?

<h2>Answers:</h2>

<h3>A. 120 cm</h3>

#CarryOnLearning

7 0
2 years ago
Draw the molecule by placing atoms on the grid and connecting them with bonds. Include all lone pairs of electrons. Show the for
Alexus [3.1K]

Answer:

See explanation below

Explanation:

In this case, let's see both molecules per separate:

In the case of SeO₂ the central atom would be the Se. The Se has oxidation states of 2+, and 4+. In this molecule it's working with the 4+, while oxygen is working with the 2- state. Now, how do we know that Se is working with that state?, simply, let's do an equation for it. We know that this molecule has a formal charge of 0, so:

Se = x

O = -2

x + (-2)*2 = 0

x - 4 = 0

x = +4.

Therefore, Selenium is working with +4 state, the only way to bond this molecule is with a covalent bond, and in the case of the oxygen will be with double bond. See picture below.

In the case of CO₂ happens something similar. Carbon is working with +4 state, so in order to stabilize the charges, it has to be bonded with double bonds with both oxygens. The picture below shows.

5 0
3 years ago
Other questions:
  • The flavor and odor of fruits comes primarily from the esters they contain. For example, a major component in the flavor of oran
    9·1 answer
  • Science need help now plz wut?
    10·2 answers
  • What causes the salinity of ocean water to decrease
    12·2 answers
  • Which equations represent precipitation reactions?
    7·1 answer
  • Recall that atoms gain or lose electrons to become ions. So, an ion has a different number of electrons than its corresponding n
    5·1 answer
  • A system conducts 50. J heat to the surroundings while delivering 20. J of work. What is the change in internal energy
    11·1 answer
  • Decay chains exist because
    11·1 answer
  • 2. What is the final temperature when a 32.0 g piece of diamond at 33.5°C is heated with 360 J of energy?
    5·1 answer
  • Which statement correctly describes gravity?
    15·2 answers
  • (ii) Calculate the maximum mass of ethanol that could be obtained<br> g from 30.0 g of glucose.
    11·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!