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3 years ago

Calculate the pH of a solution if the concentration of hydroxide ions (OH-) is 3.6 x 10-11M?

Chemistry

1 answer:

baherus [9]3 years ago

7 0

Answer:

3.56

Explanation:

pH refers to a measure of hydrogen ion concentration. It measures acidity or alkalinity of a solution. It usually ranges from 0 to 14.

If pH of aqueous solutions at 25°C is less than 7 then they are acidic, while aqueous solutions with a pH greater than 7 are alkaline.

Concentration of hydroxide ions = $3.6\times 10^{-11}$

pH = $-log \left ( 3.6\times 10^{-11} \right )=10.44$

pOH = 14 - pH = 14 - 10.44 = 3.56

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In order to prepare very dilute solutions, a lab technician chooses to perform a series of dilutions instead of measuring a very

SVETLANKA909090 [29]

Answer: The final concentration of potassium nitrate is $5.70\times 10^{-6}M$

Explanation:

To calculate the molecular mass of solute, we use the equation used to calculate the molarity of solution:

$\text{Molarity of the solution}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}$

We are given:

Mass of potassium nitrate (solute) = 0.360 g

Molar mass of potassium nitrate = 101.1 g/mol

Volume of solution = 500.0 mL

Putting values in above equation, we get:

$\text{Molarity of }KNO_3=\frac{0.360\times 1000}{101.1\times 500.0}\\\\\text{Molarity of }KNO_3=7.12\times 10^{-3}M$

To calculate the molarity of the diluted solution, we use the equation:

$M_1V_1=M_2V_2$ .......(1)

Calculating for first dilution:

$M_1\text{ and }V_1$ are the molarity and volume of the concentrated $KNO_3$ solution

$M_2\text{ and }V_2$ are the molarity and volume of diluted $KNO_3$ solution

We are given:

$M_1=7.12\times 10^{-3}M\\V_1=10mL\\M_2=?M\\V_2=500.0mL$

Putting values in equation 1, we get:

$7.12\times 10^{-3}\times 10=M_2\times 500\\\\M_2=\frac{7.12\times 10^{-3}\times 10}{500}=1.424\times 10^{-4}M$

Calculating for second dilution:

$M_2\text{ and }V_2$ are the molarity and volume of the concentrated $KNO_3$ solution

$M_3\text{ and }V_3$ are the molarity and volume of diluted $KNO_3$ solution

We are given:

$M_2=1.424\times 10^{-4}M\\V_2=10mL\\M_3=?M\\V_3=250.0mL$

Putting values in equation 1, we get:

$1.424\times 10^{-4}\times 10=M_3\times 250\\\\M_3=\frac{1.424\times 10^{-4}\times 10}{250}=5.70\times 10^{-6}M$

Hence, the final concentration of potassium nitrate is $5.70\times 10^{-6}M$

8 0

3 years ago

The thermite reaction reacts iron (III) oxide, Fe2O3, with aluminium powder,Al, the form aluminium oxide, Al2O3 and iron, Fe.

lara [203]

Answer:

This answer assumes that the strated "16.0g of iron" was meant to be 16.0 grams of iron(III) oxide.

Explanation:

To start, the thermite equation must be balanced.

I find:

1Fe2O3 + 2Al = 1Al2O3 + 2Fe

This tells us we need 2 moles of Al for every 1 mole of Fe2O3.

Now calculate the moles of each reactant:

Moles Fe2O3: 16.0 g/159.7 g/mole = 0.100 moles Fe2O3

Moles Al: 8.1 /26.98 g/mole = 0.300 moles Al

The balanced equation says that in order to react all of the Fe2O3 we'd need twice that amount (in moles) of the Al. (0.100 moles Fe2O3)*(2) = 0.200 moles Al.

Which of the two reactants is the limiting reagent?

We have more than enough moles of Al to react with 0.10 moles of Fe2O3. (We have 0.300 moles Al and all we need is 0.200 moles to react with the 0.10 moles of Fe2O3. Fe2O3 is the limiting reagent.

Calculate the maximum mass of iron of iron that could be formed using these quantities of reactants.

The balanced equation tells us that we will obtain 2 moles of Fe for every 1 mole of Fe2O3 consumed. Since Fe2O3 is the limiting reagent, we will assume that it completely reacts. That means 0.1 moles of Fe2O3 is reacted. Since we expect twice that many moles of Fe, we should obtain 0.200 moles of Fe. At 55.85 g/mole, we should obtain:

(0.200 moles Fe)*(55.85 g Fe/mole Fe) = 11.2 grams Fe

5 0

2 years ago

An atom of argon has a radius rar = 88 pm and an average speed in the gas phase at 25°C of 172 m/s.

Rudik [331]

Answer:

1.2* 10³ rNe.

Explanation:

Given speed of neon=350 m/s

Un-certainity in speed= (0.01/100) *350 =0.035 m/s

As per heisenberg uncertainity principle

Δx*mΔv ≥\frac{h}{4\pi }

4π

..................(1)

mass of neon atom =\frac{20*10^{-3} }{6.22*10^{-23} } =3.35*10^{-26} kg

6.22∗10

−23

20∗10

−3

=3.35∗10

−26

substituating the values in eq. (1)

Δx =4.49*10^{-8}10

−8

In terms of rNe i.e 38 pm= 38*10^{-12}10

−12

Δx=\frac{4.49*10^{-8} }{38*10^{-12} }

38∗10

−12

4.49∗10

−8

=0.118*10^{4}10

* (rNe)

=1.18*10³ rN

= 1.2* 10³ rNe.

Explanation:

This is the answer

7 0

3 years ago

How do substances change into different substances during chemical reactions

icang [17]

Answer:

Chemical reaction are irreversible. Some of the example of chemical reaction are cooking, rusting, and burning. During a chemical reaction, the composition of substances changes and the particles rearrange to form a new substance. The new substance formed after chemical reaction of substance has different physical and chemical properties.

When a chemical reaction occur, the atoms or molecules of the substances change its physical and chemical properties such as while cooking of vegetable, the molecules of vegetable undergo changes in their properties and form a new substance which is different from the earlier.

6 0

3 years ago

Find the volume of a gas if 3.6 mols of the gas is at STP

Digiron [165]

Answer:

81 L gas

General Formulas and Concepts:

Ideal Gas Law

STP (Standard Conditions for Temperature and Pressure) = 22.4 L per mole at 1 atm, 273 K

Stoichiometry

Using Dimensional Analysis

Explanation:

Step 1: Define

[Given] 3.6 mols gas at STP

[Solve] volume (L) of gas

Step 2: Convert

[DA] Set up: $\displaystyle 3.6 \ mol \ gas(\frac{22.4 \ L \ gas}{1 \ mol \ gas \ at \ STP})$
[DA] Multiply [Cancel out units]: $\displaystyle 80.64 \ L \ gas$

Step 3: Check

Follow sig fig rules and round. We are given 2 sig figs.

80.64 L gas ≈ 81 L gas

6 0

3 years ago