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3 years ago

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a 9.56g sample of CuS is found to contain 6.35g of copper. What is the percent by mass of sulfur in this compound? Report your a

nswer to the hundredths place

1 answer:

Volgvan3 years ago

3 0

Answer:

33.58%

Explanation:

Data obtained from the question include:

Mass of CuS = 9.56g

Mass of Cu = 6.35g

Mass of S = Mass of CuS — Mass and Cu

Mass of S = 9.56 — 6.35

Mass of S = 3.21g

The percentage by mass of sulphur in CuS is given by:

Mass of S/mass of CuS x 100

Percentage by mass of S = 3.21/9.56 x 100 = 33.58%

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An unknown salt is either NaF, NaCl, or NaOCl. When 0.050 mol of the salt is dissolved in water to form 0.500 L of solution, the

victus00 [196]

<u>Answer:</u> The unknown salt is NaF

<u>Explanation:</u>

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

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

Moles of salt = 0.050 moles

Volume of solution = 0.500 L

Putting values in above equation, we get:

$\text{Molarity of salt}=\frac{0.050mol}{0.500L}\\\\\text{Molarity of salt}=0.1M$

To calculate the hydroxide ion concentration, we first calculate pOH of the solution, which is:

pH + pOH = 14

We are given:

pH = 8.08

$pOH=14-8.08=5.92$

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

$pOH=-\log[OH^-]$

Putting values in above equation, we get:

$5.92=-\log[OH^-]$

$[OH^-]=10^{-5.92}=1.202\times 10^{-6}M$

The unknown salt given are formed by the combination of weak acid and strong acid which is NaOH

The chemical equation for the hydrolysis of $X^-$ ions follows:

$X^-(aq.)+H_2O(l)\rightleftharpoons HX(aq.)+OH^-(aq.);K_b$

<u>Initial:</u> 0.1

<u>At eqllm:</u> 0.1-x x x

Concentration of $OH^-=x=1.202\times 10^{-6}M$

The expression of $K_b$ for above equation follows:

$K_b=\frac{[OH^-][HX]}{[X^-]}$

Putting values in above expression, we get:

$K_b=\frac{(1.202\times 10^{-6})\times (1.202\times 10^{-6})}{(1-(1.202\times 10^{-6}))}\\\\K_b=1.445\times 10^{-11}M$

To calculate the acid dissociation constant for the given base dissociation constant, we use the equation:

$K_w=K_b\times K_a$

where,

$K_w$ = Ionic product of water = $10^{-14}$

$K_a$ = Acid dissociation constant

$K_b$ = Base dissociation constant = $1.445\times 10^{-11}$

Putting values in above equation, we get:

$10^{-14}=1.445\times 10^{-11}\times K_a\\\\K_a=\frac{10^{-14}}{1.445\times 10^{-11}}=6.92\times 10^{-4}$

We know that:

$K_a\text{ for HF}=6.8\times 10^{-6}$

$K_a\text{ for HCl}=1.3\times 10^{6}$

$K_a\text{ for HClO}=3.0\times 10^{-8}$

So, the calculated $K_a$ is approximately equal to the $K_a$ of HF

Hence, the unknown salt is NaF

6 0

2 years ago

In the reaction H2SO4 + 2 NaOH -> Na2SO4 + 2H2O, an equivalence point occurs when 29.43 mL of 0.1973 M NaOH is added to a 32.

Tamiku [17]

            moles NaOH = c · V = 0.1973 mmol/mL · 29.43 mL = 5.806539 mmol
            moles H2SO4 = 5.806539 mmol NaOH · 1 mmol H2SO4 / 2 mmol NaOH = 2.9032695 mmol
Hence
            [H2SO4]= n/V = 2.9032695 mmol / 32.42 mL = 0.08955 M
The answer to this question is [H2SO4] = 0.08955 M

6 0

2 years ago

Sodas are made fizzy by the carbon dioxide ( CO ) dissolved in the liquid. An amount of carbon 2 dioxide equal to about 8.0 L of

eduard

Answer:

A) The number of moles of Carbon dioxide in 2.0 L bottle of soda = 0.325 mole

B) The mass of Carbon dioxide in 2.0 L bottle of soda = 14.3 g

Explanation:

Complete Question

Soda are made fizzy by the carbon dioxide (CO₂) dissolved int he liquid. An amount of carbon dioxide equal to about 8.0 L of carbon dioxide gas at atmospheric pressure and 300.0 K can be dissolved can be dissolved in a 2-L bottle of soda. The molar mass of CO₂ IS 44 g/mol.

A) How many moles of carbon dioxode are in the 2-L? (1L = 0.001 m³)

B) What is the mass of the carbon dioxide in the 2-L bottle of soda?

Solution

Assuming that CO₂ is an ideal gas.

A) The amount of carbon dioxide in 2.0 L of soda bottle is equal to the amount of Carbon dioxide in about 8.0 L of carbon dioxide gas at atmospheric pressure and 300.0 K

From the ideal gas equation, we know that

PV = nRT

P = pressure of the gas = atmospheric pressure = 101,325 Pa

V = volume of the gas = 8.0 L = 0.008 m³

n = number of moles of the ideal gas = ?

R = molar gas constant = 8.314 J/mol.K

T = absolute temperature of the gas in Kelvin = 300 K

101325 × 0.008 = n × 8.314 × 300

n = (101325×0.008) ÷ (8.314 × 300)

n = 0.324993986 = 0.325 mole of Carbon dioxide.

B) The mass of Carbon dioxide in 2.0 L bottle of soda

Mass = (Number of moles) × (Molar mass)

= 0.325 × 44.0

= 14.3 g

Hope this Helps!!!

7 0

2 years ago

Show the difference in the reactivity of Na,Ca,Mg,Al,Fe,Cu with H2O

Vesnalui [34]

Answer:

Explanation:

Na react with H2O to form NAOH

2 Na+2H2O....................2NAOH + H2

Ca react with water and form calcium hydroxide

Ca + 2H2O........................Ca(OH)2

Mg react with water and form Magnesium hydroxide

Mg +2H2O .........................Mg(OH)2 however this coating of mg(oh)2 prevent it from further reaction

Fe react with water and form ferric hydride

3Fe +H2O.......................2 FeH +FeO

copper do not react with water

7 0

3 years ago

If you have 400 grams of a substance that decays with a half-life of 14 days, then how much will you have after 56 days? To help

alisha [4.7K]

Answer:

25 grams

Explanation:

You strat off with 400 grams of your substance. By day 14, half has dcayed and you only have 200 grams left. By day 28, there are 100 grams of the substance. On day 42, there are 50 grams left. Finally, on day 56, the substance has been through four half-lives and 25 grams remain.

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2 years ago