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Fed [463]
2 years ago
13

A 5.0 g sample of calcium nitrate (Ca(NO3)2, M = 164) contaminated with silica (SiO2, M = 60.1) is found to contain 1.0 g calciu

m. What is the mass percent purity of calcium nitrate in the sample?
Chemistry
1 answer:
zhenek [66]2 years ago
4 0

Answer:

= 82%

Explanation:

Percentage purity is calculated by the formula;

% purity = (mass of pure chemical/total mass of sample) × 100

In this case;

1 mole of Ca(NO3)2 = 164 g

but; 164 g of Ca(NO3)2 = 40 g Ca

Therefore; mass of Ca(NO3)2 = 164 /40

                                                  = 4.1 g

Thus;

% purity of Ca(NO3)2 = (Mass of Ca(NO3)2/ mass of the sample)× 100

                                    = (4.1 g/ 5 g) × 100

                                    = 82%

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consider the reaction between sulfite and a metal anion, X2-, to form the metal, X, and thiosulfate: 2 X2-(aq) + 2 SO32- + 3 H2O
Dafna11 [192]

Answer:

E_{red}^{0} for X is -1.20 V

Explanation:

Oxidation: 2\times[X^{2-}(aq.)-2e^{-}\rightarrow X(s)]

reduction: 2SO_{3}^{2-}(aq.)+3H_{2}O(l)+4e^{-}\rightarrow S_{2}O_{3}^{2-}(aq.)+6OH^{-}(aq.)

---------------------------------------------------------------------------------------------------

overall:2X^{2-}(aq.)+2SO_{3}^{2-}(aq.)+3H_{2}O(l)\rightarrow 2X(s)+S_{2}O_{3}^{2-}(aq.)+6OH^{-}(aq.)

So, E_{cell}^{0}=E_{red}^{0}(SO_{3}^{2-}\mid S_{2}O_{3}^{2-})-E_{red}^{0}(X\mid X^{2-})

or, 0.63=-0.57-E_{red}^{0}(X\mid X^{2-})

or, E_{red}^{0}(X\mid X^{2-})= -1.20

So, E_{red}^{0} for X is -1.20 V

8 0
2 years ago
Read 2 more answers
How many Ca2+ ions are in a sample of CaSO4 having a total mass of 68.07 g?
harkovskaia [24]

Answer:

There are  

17.01

Explanation:

The chemical formula for calcium phosphate is  

Ca

3

(PO

4

)

2

. This means that in one mole of calcium phosphate, there are three calcium ions and two phosphate ions.

6 0
2 years ago
Two weak acids, A and B, have pKa values of 4 and 6, respectively. Which statement is true?A) Acid A dissociates to a greater ex
zalisa [80]

Answer:

A) Acid A dissociates to a greater extent in water than acid B

Explanation:

A) Acid A dissociates to a greater extent in water than acid B

We are given the pKa for both acids, and we know

pKa = - log Ka

Taking antilog to both sides of the equation we can solve for Ka

⇒ -pKa = log Ka

-antilog pKa = Ka

10 ^-pka = Ka

So ka for acid A = 10⁻⁴

and

ka for acid B = 10⁻⁶

True the equilibrium constant for acid A is greater, so it dissociates more.

B) For solutions of equal concentration, acid B will have a lower pH.

We know the stronger acid is A, and it dissociates more. Since pH is the negative log of H₃O⁺ concentration, it follows that at equal concentrations the acid A will have at equilibrium a greater [H₃O⁺] and hence a lower pH

C) B is the conjugate base of A

False:

If B were the conjugate base of A, its  Kb would have been given by:

Ka x Kb = Kw

Kb = 10⁻¹⁴/10⁻⁶ = 10⁻⁸ for the conjugate base of acid B

Kb = 10⁻¹⁴/10⁻⁴ = 10⁻¹⁰ for the conjugate base of acid A

which are not equal.

D) Acid A is more likely to be a polyprotic acid than acid B.

False

Just having the pkas for both acids one cannot know if any of the acids is polyprotic. We will need the formula for the acids.

E) The equivalence point of acid A is higher than that of acid B

False

The equivalence point depends on the the concentration of the acids  and their volumes.

The equivalence point is reached in the titration when the number of equivalents of base equals the number of equivalents of acid:

# equivalents acid = # equivalents of base  @ end point

and

# equivalents acid = Molarity of acid x Volume of acid

4 0
2 years ago
A balance measures mass to 0.001 g. If you determine the mass of an object that weighs about 30 g, would you record the mass as
solong [7]

Answer:

The mass is recorded as 32.075 g

Explanation:

"The first digit of uncertainty is taken as the last significant digit", this is the rule for significant figures in the analysis. The balance measures the mass up to three decimal places, so it makes the most sense to note the  whole figure.

8 0
2 years ago
Read 2 more answers
A chemist wants to extract copper metal from copper chloride solution. The chemist places 1.50 grams of aluminum foil in a solut
Lisa [10]

Answer: d. More than 6.5 grams of copper (II) is formed, and some copper chloride is left in the reaction mixture.

Explanation: 2Al+3CuCl_2\rightarrow 2AlCl_3+3Cu

As can be seen from the chemical equation, 2 moles of aluminium react with 3 moles of copper chloride.

According to mole concept, 1 mole of every substance weighs equal to its molar mass.

Aluminium is the limiting reagent as it limits the formation of product and copper chloride is the excess reagent as (14-7.5)=6.5 g is left as such.

Thus 54 g of of aluminium react with 270 g of copper chloride.

1.50 g of aluminium react with=\frac{270}{54}\times 1.50=7.5 gof copper chloride.

3 moles of copper chloride gives 3 moles of copper.

7.5 g of copper chloride gives 7.5 g of copper.

8 0
2 years ago
Read 2 more answers
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