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jonny [76]
3 years ago
6

1. A 5.05 g sample of quartz (SiO2) contains 2.36 g of silicon. What are the percentages of silicon

Chemistry
1 answer:
hammer [34]3 years ago
6 0

Answer: B) 46.7% Si and 53.3% O

Explanation:

To calculate the mass percent of element in a given compound, we use the formula:

\text{Mass percent of element}=\frac{\text{Mass of element}}{\text{total mass}}\times 100\%

Mass of quartz  (SiO_2) = 5.05 g

Mass of silicon = 2.36 g

Mass of oxygen = Mass of quartz  (SiO_2) - mass of silicon = 5.05g - 2.36 g = 2.69 g

\text{Mass percent of silicon}=\frac{\text{Mass of silicon}}{\text{total mass of quartz}}\times 100=\frac{2.36}{5.05}\times 100=46.7\%

\text{Mass percent of oxygen}=\frac{\text{Mass of oxygen}}{\text{total mass of quartz}}\times 100=\frac{2.69}{5.05}\times 100=53.3\%

Thus the percentages of silicon and oxygen in quartz are B) 46.7% Si and 53.3% O

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A standard galvanic cell is constructed so that the overall cell reaction is as given below where M is an unknown metal. 2 Al3+(
jasenka [17]

Answer:

magnesium metal

Explanation:

According to the redox reaction equation, six electrons were transferred hence n=6 and F= Faraday's constant 96500C. ∆G° is given hence E°cell can easily be calculated as follows:

From ∆G°= -nFE°cell

E°cell= -∆G°/nF= -(-411×10^3/96500×6)

E°cell= 0.7098V

But for Al3+(aq)/Al(s) half cell, E°= -1.66V from standard table of reduction potentials.

E°cell= E°cathode- E°anode but Al3+(aq)/Al(s) half cell is the cathode

Hence

E°anode=E°cathode - E°cell

E°anode= -1.66-0.7098= -2.37V

This is the reduction potential of Mg hence the anode material was magnesium metal

5 0
3 years ago
When 1.104 grams of iron metal are mixed with 26.023 grams of hydrochloric acid in a coffee cup calorimeter, the temperature ris
Alika [10]

Answer:

a) An exothermic reaction, will release heat. No heat will be absorbed.

b) 903.71 J  of heat released

c) reaction is exothermic and ∆H will be negative.

d) ΔHreaction = 818.6 J/g

e)  ΔHreaction = 45.6 kJ/mol

f) ΔHreaction = 91.2 kJ

Explanation:

<u>Step 1:</u> Data given

Mass of iron = 1.104 grams

Mass of hydrochloric acid = 26.023 grams

Initial temperature = 25.2°C

Final temperature = 33.5 °C

Temperature change = 8.3 °C

<u>Step 2:</u> The balanced equation

2Fe(s)+6HCl(aq) → 2FeCl3 (aq)+3H2 (g)

(A)  Determine the amount of heat (in J) absorbed by the reaction mixture.

Since we have a rise of temperature, this means the reaction is exothermic.

An exothermic reaction, will release heat. No heat will be absorbed.

(B)  How much heat (in J) was released by the reaction that occurred?

q = mC∆T

with q = heat released (in J)

with m = the mass (in grams)

with c = the specific heat capacity (in J/g°C)

with  ∆T  = The change in temperature (in °C)

q = (26.023g)*(4.184 J/g°C)*(8.3 °C) = 903.71 J  of heat released

(C)  Is this reaction exothermic or endothermic? Is ΔHreaction positive or negative?

Since we have a rise of temperature, this means the reaction is exothermic.

There is heat released so ∆H will be negative.

(D)  Under constant pressure conditions (as used in this experiment), the heat released by the reaction equals the reaction enthalpy, qreleased = ΔHreaction. Determine ΔHreaction in Joules per gram of metal used (J/g).

ΔHreaction = 903.71 J/1.104 g = 818.6 J/g

(E) Determine ΔHreaction in kilojoules per mole of metal used (kJ/mol)

Number of moles of iron =1.104 grams / 55.845 g/mol = 0.0198 moles

ΔHreaction = 903.71 J / 0.0198 moles = 45641.9 J/mol = 45.6 kJ/mol

(F)  Determine ΔHreaction in kilojoules per mole for the balanced reaction equation provided

Since we have 2moles of Fe in the balanced reaction;

ΔHreaction = 45.6 kJ/mol * 2 mol = 91.2 kJ

7 0
3 years ago
How do SMRs provide more flexibility than ordinary nuclear reactors?
Shkiper50 [21]

Answer:

The SMRs can adjust their energy output using coolants and control rods.

Power plants can be built to fit locations with less demand or less space.

Explanation:

I think that it is but I am not sure.

7 0
3 years ago
Whenever a number or a variable is divided<br> by itself, it is always equal to
Jobisdone [24]

Answer:itself

Explanation:

Duh

5 0
3 years ago
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kiruha [24]
About 75% of earth’s surface is covered by the ocean
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