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3241004551 [841]

3 years ago

15

Câu 3: Nêu phương pháp hóa học nhận biết các dung dịch không màu sau: (a) HCI, NaOH, H2SO,, NaCl. (b) HNO3. KOH, BaCl. Ca(OH)2.

Ba(NO3)2 (c) MgCl2, KCl, CuCl2, FeCl3, FeCl2 (chỉ dùng một thuốc thử). (d) Na2CO3, BaCl2, NaNO3 (chỉ dùng một thuốc thử)

1 answer:

True [87]3 years ago

5 0

Answer:

uvo 8hih8hjfiuwubosbwbhp0heg

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If 45.0 mL of ethanol (density = 0.789 g/mL) initially at 8.0 ∘C is mixed with 45.0 mL of water (density = 1.0 g/mL) initially a

strojnjashka [21]

Answer : The final temperature of the mixture is, $22.14^oC$

Explanation :

First we have to calculate the mass of ethanol and water.

$\text{Mass of ethanol}=\text{Density of ethanol}\times \text{Volume of ethanol}=0.789g/mL\times 45.0mL=35.5g$

and,

$\text{Mass of water}=\text{Density of water}\times \text{Volume of water}=1.0g/mL\times 45.0mL=45.0g$

Now we have to calculate the final temperature of the mixture.

In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.

$q_1=-q_2$

$m_1\times c_1\times (T_f-T_1)=-m_2\times c_2\times (T_f-T_2)$

where,

$c_1$ = specific heat of ethanol = $2.42J/g^oC$

$c_2$ = specific heat of water = $4.18J/g^oC$

$m_1$ = mass of ethanol = 35.5 g

$m_2$ = mass of water = 45.0 g

$T_f$ = final temperature of mixture = ?

$T_1$ = initial temperature of ethanol = $8.0^oC$

$T_2$ = initial temperature of water = $28.6^oC$

Now put all the given values in the above formula, we get:

$35.5g\times 2.42J/g^oC\times (T_f-8.0)^oC=-45.0g\times 4.18J/g^oC\times (T_f-28.6)^oC$

$T_f=22.14^oC$

Therefore, the final temperature of the mixture is, $22.14^oC$

3 0

4 years ago

A 4.0 L container holds a sample of hydrogen gas at 306 K and 150 kPa. If the pressure increases to 300 kPa and the volume remai

riadik2000 [5.3K]

Answer:

612 K

Explanation:

From the question given above, the following data were obtained:

Initial temperature (T₁) = 306 K

Initial pressure (P₁) = 150 kPa

Final pressure (P₂) = 300 kPa

Volume = 4 L = constant

Final temperature (T₂) =?

Since the volume is constant, the final (i.e the new) temperature of the gas can be obtained as follow:

P₁ / T₁ = P₂ / T₂

150 / 306 = 300 / T₂

Cross multiply

150 × T₂ = 306 × 300

150 × T₂ = 91800

Divide both side by 150

T₂ = 91800 / 150

T₂ = 612 K

Thus, the new temperature of the gas is 612 K

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3 years ago

Which statement accurately describes non renewable energy sources ?

xz_007 [3.2K]

a resource that cannot be replenished in a short period of time

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4 years ago

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The Law of _____states that substances combine in predictable proportions and that excess reactants remain unchanged.

RideAnS [48]

Answer: definite proportions.

Explanation:

1) The definite proportions law states that compounds will always have the same kind of atoms (elements) in the same mass proportion (ratios).

2) For example, a molecule of water will alwys have the same mass ratio of hydrogen atoms to oxygen atoms. That is what permits to obtain the chemical formula of the water molecule as H₂O.

The mass of the two hydrogen atoms will be in a fixed ratio respect to the mass of the oxygen atoms.

Then, if you have one reactant in less proportion than the other, respect to the ratio stated by the chemical formula of water, the former will react completely (it is the limiting reactant) with the corresponding (proportional) mass of the later. Then there will be an excess of the later reactant which will not react (will remain unchanged).

The reactants can only react in the proportion defined by the chemical formulas of the final products.

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3 years ago

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Which substance is not a structural isomer of hexyne?

stich3 [128]

Answer:

c) 3,3-dimethylpent-1-yne

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3 years ago