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1 year ago

You need to prepare 2.00 L of 0.100 M Na2CO3 solution. The best procedure is to weigh out: ___________

Chemistry

2 answers:

lyudmila [28]1 year ago

7 0

It would be C I believe

jeka941 year ago

4 0

Answer:

The answer to your question is letter C

Explanation:

Data

Volume = 2 L

Molarity = 0.100 M

Molecular weight Na₂CO₃ = (2 x 23) + (1 x 12) + (3 x 16)

= 46 + 12 + 48

= 106 g

Process

1.- Calculate the grams of Na₂CO₃ needed

106 g ---------------- 1 mol

x ---------------- 0.1 moles

x = (0.1 x 106) / 1

x = 10.6 g

2.- Calculate the grams of Na₂CO₃ needed for 2 liters of solution

10.6 g -------------- 1 liter

x -------------- 2 liters

x = (10.6 x 2) / 1

x = 21.2 grams of Na₂CO₃

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Turbo the snail moves across the ground at a pace of 12 feet per day. If the garden is 48 feet away, how many days will it take

katen-ka-za [31]

Answer:4 days will it take for the snail to get to the garden.

Explanation:

Speed of the snail = 12 feet per day:

Distance between the garden and snail = 48 feet

$Speed=\frac{Distance}{Time}$

$Time=\frac{48 feet}{12 \text{feet per day}}=4 days$

4 days will it take for the snail to get to the garden.

8 0

2 years ago

A 15.0 mL sample of 0.013 M HNO3 is titrated with 0.017 M CH$NH2 which he Kb=3.9 X 10-10. Determine the pH at these points: At t

kramer

Answer: The pH of the solution in the beginning is 1.89 and the pH of the solution after the addition of base is

Explanation:

For 1: At the beginning

To calculate the pH of the solution, we use the equation:

$pH=-\log[H^+]$

We are given:

Nitric acid is a monoprotic acid and it dissociates 1 mole of hydrogen ions. So, the concentration of hydrogen ions is 0.013 M

$[H^+]=0.013M$

Putting values in above equation, we get:

$pH=-\log(0.013)\\\\pH=1.89$

For 2:

To calculate the number of moles, we use the equation:

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

For nitric acid:

Molarity of nitric acid solution = 0.013 M

Volume of solution = 15 mL

Putting values in above equation, we get:

$0.013M=\frac{\text{Moles of }HNO_3\times 1000}{15}\\\\\text{Moles of }HNO_3=1.95\times 10^{-4}mol$

For methylamine:

Molarity of methylamine solution = 0.017 M

Volume of solution = 10 mL

Putting values in above equation, we get:

$0.017M=\frac{\text{Moles of }CH_3NH_2\times 1000}{10}\\\\\text{Moles of }CH_3NH_2=1.7\times 10^{-4}mol$

The chemical equation for the reaction of nitric acid and methylamine follows:

$HNO_3+CH_3NH_2\rightarrow CH_3NH_3^++NO_3^-$

As, the mole ratio of nitric acid and methyl amine is 1 : 1. So, the limiting reagent will be the reactant whose number of moles are less, which is methyl amine.

By Stoichiometry of the reaction:

1 mole of methyl amine produces 1 mole of $CH_3NH_3^+$

So, $1.7\times 10^{-4}mol$ of methyl amine will produce = $\frac{1}{1}\times 1.7\times 10^{-4}=1.7\times 10^{-4}\text{ moles of }CH_3NH_3^+$

To calculate the $pK_b$ of base, we use the equation:

$pK_b=-\log(K_b)$

where,

$K_b$ = base dissociation constant = $3.9\times 10^{-10}$

Putting values in above equation, we get:

$pK_b=-\log(3.9\time 10^{-10})\\\\pK_b=9.41$

To calculate the pOH of basic buffer, we use the equation given by Henderson Hasselbalch:

$pOH=pK_b+\log(\frac{[salt]}{[base]})$

$pOH=pK_b+\log(\frac{[CH_3NH_3^+]}{[CH_3NH_2]})$

We are given:

$pK_b=9.41$

$[CH_3NH_3^+]=\frac{1.7\times 10^{-4}}{10+15}=6.8\times 10^{-6}M$

$[CH_3NH_2]=\frac{1.7\times 10^{-4}}{10+15}=6.8\times 10^{-6}M$

Putting values in above equation, we get:

$pOH=9.41+\log(\frac{6.8\times 10^{-6}}{6.8\times 10^{-6}})\\\\pOH=9.41$

To calculate pH of the solution, we use the equation:

$pH+pOH=14\\pH=14-9.41=4.59$

Hence, the pH of the solution is 4.59

4 0

2 years ago

A liquid mixture containing 0.50 mole fraction benzene - toluene is contained in a storage vessel at 25°C and 1 atm. The vessel

Snowcat [4.5K]

Answer:

a. Yes, it is flammable.

b. It can cause hazard and carcinogenic effect.

Explanation:

A. Yes, the vapor in the vessel is flammable because it is an organic solvent with a very low boiling point. For this reason, less energy can vaporize it. Therfore, a little high temperature or energy causes it to be very reactive and flammable.

B. - Being flammable makes it hazardous, that is, it is capable of being ignited and can burn easily, which makes it really dangerous.

- It results in carcinogenic effect on the body. Substances that cause carcinogenic effect are capable of increasing the risk of cancer. They might contain compounds that can initiate tumor.

When the temperature is high, the risk of explosion increases. Due to the fact that at higher temperature, the kinetic energy of the atoms which result in an increase in the volume and finally blasting of the vessel.

7 0

1 year ago

A hot gas flowing through a pipeline can be considered as a:________

k0ka [10]

Answer:

B) irreversible process

Explanation:

The process given here is irreversible.

7 0

2 years ago

in order to find the molar mass of an unknown compound, a research scientist prepared a solution of 0.930 g of an unknown in 125

PtichkaEL [24]

Answer:

Molar mass→ 0.930 g / 6.45×10⁻³ mol = 144.15 g/mol

Explanation:

Let's apply the formula for freezing point depression:

ΔT = Kf . m

ΔT = 74.2°C - 73.4°C → 0.8°C

Difference between the freezing T° of pure solvent and freezing T° of solution

Kf = Cryoscopic constant → 5.5°C/m

So, if we replace in the formula

ΔT = Kf . m → ΔT / Kf = m

0.8°C / 5.5 m/°C = m → 0.0516 mol/kg

These are the moles in 1 kg of solvent so let's find out the moles in our mass of solvent which is 0.125 kg

0.0516 mol/kg . 0.125 kg = 6.45×10⁻³ moles. Now we can determine the molar mass:

Molar mass (mol/kg) → 0.930 g / 6.45×10⁻³ mol = 144.15 g/mol

3 0

2 years ago