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3 years ago

What are the source of error in determination of boiling point and melting point

1 answer:

7 0

purity of the substance is usually the main error (for example: water with impurities will have m.p. less than 273K or 0 degree celcius while it's b.p. will be greater than 373K or 100 degree celcius). 
-> air/ room temperature (it takes longer to cook in mountains and shorter at beaches) 
-> parallax error (error by determining the meniscus of the thermometer) 
and many more..

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2. Consider the reaction 2 Cg H18 (4) +250â (9) âº 16 co, (g) + 18 HâO(g) la How many moles of H20co) are produced, when |--16:1

Sladkaya [172]

Answer :

(a) The moles of water produced are 145.35 moles.

(b) The mass of oxygen needed are 3080.8 grams.

Solution for part (a) : Given,

Moles of $C_8H_{18}$ = 16.15 moles

First we have to calculate the moles of $H_2O$

The balanced chemical reaction is,

$2C_8H_{18}+25O_2\rightarrow 16CO_2+18H_2O$

From the balanced reaction we conclude that

As, 2 moles of $C_8H_{18}$ react to give 18 moles of $H_2O$

So, 16.15 moles of $C_8H_{18}$ react to give $\frac{16.15}{2}\times 18=145.35$ moles of $H_2O$

The moles of water produced are 145.35 moles.

Solution for part (b) : Given,

Mass of $C_8H_{18}$ = 878 g

Molar mass of $C_8H_{18}$ = 114 g/mole

Molar mass of $O_2$ = 32 g/mole

First we have to calculate the moles of $C_8H_{18}$ .

$\text{ Moles of }C_8H_{18}=\frac{\text{ Mass of }C_8H_{18}}{\text{ Molar mass of }C_8H_{18}}=\frac{878g}{114g/mole}=7.702moles$

Now we have to calculate the moles of $O_2$

The balanced chemical reaction is,

$2C_8H_{18}+25O_2\rightarrow 16CO_2+18H_2O$

From the balanced reaction we conclude that

As, 2 moles of $C_8H_{18}$ react with 25 moles of $O_2$

So, 7.702 moles of $C_8H_{18}$ react with $\frac{7.702}{2}\times 25=96.275$ moles of $O_2$

Now we have to calculate the mass of $O_2$ .

$\text{ Mass of }O_2=\text{ Moles of }O_2\times \text{ Molar mass of }O_2$

$\text{ Mass of }O_2=(96.275moles)\times (32g/mole)=3080.8g$

The mass of oxygen needed are 3080.8 grams.

6 0

3 years ago

Explain with examples following characteristics of chemical reactions: a. Change of colour b. Evolution of gas c. Change of smel

Andrei [34K]

Answer:

Explanation:

a. change of colour:

A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products. The products have different molecular structures than the reactants. Different atoms and molecules radiate different colours of light. Hence, there usually is a change in colour during a chemical reaction.

Eg: copper reactions with the elements

b. Evolution of gas:

A gas evolution reaction is a chemical reaction in which one of the end products is a gas such as oxygen or carbon dioxide.

Eg: ammonium hydroxide breaks down to water and ammonia gas.

c. Change of smell :

Production of an Odor Some chemical changes produce new smells. ... The formation of gas bubbles is another indicator that a chemical change may have occured.

Eg: The chemical change that occurs when an egg is rotting produces the smell of sulfur.

d. Change of state:

A chemical reaction is a process in which one or more substances, also called reactants, are converted to one or more different substances, known as products.

Eg: candle wax (solid) melts initially to produce molten wax (liquid)

plz mark as brainliest!!!!

4 0

3 years ago

How many moles are in 297g of nh3? Please show work, will give brainliest.

rusak2 [61]

Answer:

17.5moles

Explanation:

The number of moles in a substance can be calculated by using the formula;

Number of moles (n) = mass (m) ÷ molar mass (MM)

According to this question, mass of ammonia (NH3) = 297g

Molar Mass of NH3 = 14 + 1(3)

= 17g/mol

n = 297/17

n = 17.47

Number of moles of NH3 = 17.5moles

3 0

3 years ago

-FeS2+-O2->-Fe2O3+-SO2 What coefficient should be placed in front of SO2 to balance the equation?

NISA [10]

Answer:

8 should be placed in front of SO₂.

Explanation:

The easiest way to solve this question is by writing the entire balanced equation:

4FeS₂ + 11O₂ -> 2Fe₂O₃ + 8SO₂

We can achieve this by first balancing the Fe, then S, and finally the O.

We can also double check our answer by counting the number of each element on both sides:

-Reactants: 4 Fe, 8 S, 22 O

-Products: 4 Fe 8 S, 22 O

Since they match, our equation is balanced, and the coefficient in front of SO₂ is 8.

8 0

3 years ago

Select the correct structure that

UkoKoshka [18]

Answer:

ugh this wont save anyway i think i'm just checking if ill save

Explanation:

if i does C both

hope this helps

6 0

3 years ago