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3 years ago

A solution that contains 7 moles of solute dissolved in 20 liters of solution has a molarity of

Chemistry

1 answer:

slava [35]3 years ago

4 0

Answer:

The molarity is 0,35M

Explanation:

The molartity is moles of compound in 1 liter of solution :

20 L----------7moles compound

1 L..-----------x= (1L x7 moles compound )/20L= 0,35 moles compound--> 0,35M

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How many molecules of oxygen are produced when a sample of 38.9 g of water is decomposed by electricity?

statuscvo [17]

Answer:

A) $6.5\times 10^{23}\ \text{molecules}$

Explanation:

m = Mass of water = 38.9

M = Molar mass of water = 18 g/mol

$N_A$ = Avogadro's number = $6.022\times 10^{23}\ \text{mol}^{-1}$

The reaction of electrolysis would be

$2H_2O(l)\rightarrow 2H_2(g)+O_2(g)$

Number of moles of $H_2O$

$n=\dfrac{m}{M}\\\Rightarrow n=\dfrac{38.9}{18}\ \text{mol}$

From the reaction it can be seen that 2 moles of $H_2O$ gives 1 mole of $O_2$

So, number of moles of $O_2$ produced is

$\dfrac{38.9}{18}\times \dfrac{1}{2}=1.081\ \text{mol}$

Number of molecules

$1.081N_A=1.081\times 6.022\times 10^{23}\\ =6.5\times 10^{23}$

So, $6.5\times 10^{23}\ \text{molecules}$ of oxygen is produced.

8 0

2 years ago

Ano ang kaganapan na nangyari at nasabing nagsimula ang holy ramon empire

Ksenya-84 [330]

Answer:

plzz give the question in English

5 0

3 years ago

2. Problem: Is colored or black and white text more easily remembered? Hypothesis: If the text is colored, then the text is more

Varvara68 [4.7K]

Answer:

This question contains a lot of subsections. Please find the variables to each question below

Explanation:

Hypothesis is a testable explanation to a scientific question. It aims at proffering a testable solution to an observed problem. It usually goes in an IF, THEN format.

Dependent variable is the variable being measured in an experiment, while the independent variable is the variable that is manipulated or changed by the experimenter.

The control group is the group that does not receive the experimental treatment while constant is the variable that is kept unchanged for all groups in the experiment.

Based on this explanation, find the answers to the hypothesis, independent variable, dependent variable, constant, and control groups to each question.

2. Dependent variable: How easy it is to remember

Independent variable: Color of the text

Control: Group given Black and White text to read

Constants: Same text

3. Hypothesis: If the temperature is increased, THEN the speed of ants increases or move faster

Independent variable: TEMPERATURE

Dependent variable: SPEED OF ANTS

Control: Ants placed in room temperature

Constants: SAME KIND OF ANTS

4. Hypothesis: IF the pH of the soil is acidic or alkaline, THEN the growth of strawberries will be inhibited

Independent variable: pH of soil

Dependent variable: Growth of strawberries

Control: Strawberries grown in a Neutral pH soil

Constants: Same type of plants (strawberries)

5. Hypothesis: IF caffeine is taken, then the blood pressure will be increased or raised.

Independent variable: CAFFEINE

Dependent variable: BLOOD PRESSURE

Control: Group given no caffeine

Constants: Same amount of caffeine

6. Hypothesis: IF music is played, THEN the heart rate increases

Independent variable: MUSIC

Dependent variable: HEART RATE

Control: Groups placed where no music is played

Constants: Same type of music, same time music runs for etc.

7. Hypothesis: IF bleach is present/used, THEN bacteria will die

Independent variable: Bleach

Dependent variable: Death of bacteria

Control: Bacteria given no bleach

Constants: Same species of bacteria, Same type of bleach

3 0

3 years ago

1) What mass of Na2CO3 is required to make 50cc of its seminormal solution?

love history [14]

Answer:

$m=1.325gNa_2CO_3$

Explanation:

Hello,

In this case, by considering the given seminormal solution, we infer it is a 0.5-N solution which means that we can obtain the equivalent grams as shown below for the 55 cc (0.055 L) volume:

$eq-g=0.5eq-g/L*0.050L=0.025eq-g$

Next, since sodium carbonate has two sodium ions with a +1 oxidation state each, we can obtain the moles:

$mol=0.025eq-gNa_2CO_3*\frac{1molNa_2CO_3}{2eq-gNa_2CO_3}\\ \\mol=0.0125molNa_2CO_3$

Finally, the mass is computed by using its molar mass (106 g/mol)

$m=0.0125molNa_2CO_3*\frac{106gNa_2CO_3}{1molNa_2CO_3} \\\\m=1.325gNa_2CO_3$

Regards.

7 0

3 years ago

a) What substances are present in an aqueous buffer composed of HC2H3O2 and C2H3O2 - ?b) What happens when LiOH is added to a bu

Alex17521 [72]

Answer:

a) HC₂H₃O₂, C₂H₃O₂⁻, H₃O⁺, H₂O, OH⁻

b) HC₂H₃O₂ + LiOH ⇄ H₂O + LiC₂H₃O₂

c) C₂H₃O₂⁻ + HBr ⇄ HC₂H₃O₂ + Br⁻

Explanation:

a) In a HC₂H₃O₂/C₂H₃O₂⁻ buffer system, the following reactions take place:

HC₂H₃O₂ + H₂O ⇄ C₂H₃O₂⁻ + H₃O⁺

C₂H₃O₂⁻ + H₂O ⇄ HC₂H₃O₂ + OH⁻

Thus, the species present are: HC₂H₃O₂, C₂H₃O₂⁻, H₃O⁺, H₂O, OH⁻.

b) When LiOH is added to the buffer system, it is partially neutralized according to the following equation.

HC₂H₃O₂ + LiOH ⇄ H₂O + LiC₂H₃O₂

c) When HBr is added to the buffer system, it is partially neutralized according to the following equation.

C₂H₃O₂⁻ + HBr ⇄ HC₂H₃O₂ + Br⁻

3 0

3 years ago