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3 years ago

(08.04 MC)

Chemistry

1 answer:

Veronika [31]3 years ago

5 0

Answer:

Both have a pH greater than 7, but NH₃ has a lower pH than KOH.

Explanation:

Both of NH₃ and KOH are bases (can produce OH⁻), so both have a pH greater than 7.

NH₃ is considered as a weak base (not completely ionized), while KOH is a strong base (completely ionized).

If both NH₃ an KOH has the same concentration, KOH produces OH⁻ higher than that of NH₃.

So, NH₃ has a lower pH than KOH.

Thus the right choice is:

Both have a pH greater than 7, but NH₃ has a lower pH than KOH.

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The correct answer is A, B and C

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A balloon is filled with 2.5 L of helium at 1 atm of pressure. If the pressure

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Answer:

5 L

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Final volume (V₂): ?

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Explain the concept: Law of Multiple Proportions. Short and simple please

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A large pot (10 kg) of beef stew is left out on the kitchen counter to cool. The rate of cooling, in kJ/min, equals 1.955 (T-25)

olga_2 [115]

Answer:

16 minutes

Explanation:

First, we need to calculate the amount of heat needed to cool the beef stew:

Q = mcΔT

Where m is the mass, c is the heat capacity and ΔT is the variation of the temperature.

Q = 10x4x(40 - 90)

Q = -2000 kJ

So, the beef stew needs to lost 2000 kJ to cool.

With the initial temperature at 90ºC, the rate of cooling(r) will be:

r = 1.955x(90 - 25)

r = 127.075 kJ/min

So, to lose 2000 kJ, will be necessary:

t = Q/r

t = 2000/127.075

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3 years ago

Alum is a compound used in a variety of applications including cosmetics, water purification, and as a food additive. It can be

vlabodo [156]

Answer:

The theoretical yield of alum is 19.873 grams and percent yield for this alum synthesis is 45.33%.

Explanation:

Mass of bottle = 10.221 g

Mass of bottle with aluminium pieces = 11.353 g

Mass of aluminium = 11.353 g - 10.221 g = 1.132 g

Mass of alum and bottle = 19.230 g

Mass of alum = 19.230 g - 10.221 g = 9.009 g

Experimental yield of alum = 9.009 g

Theoretical yield of alum:

$2Al(s) +2 KOH(aq) +4H_2SO_4(aq)+10 H_2O(l) \rightarrow 2 KAl(SO_4)_2.12 H_2O(s)+3H_2(g)$

Moles of aluminium = $\frac{1.132 g}{27 g/mol}=0.041926 mol$

According to reaction, 2 moles of aluminum gives 2 moles of alum.

Then 0.041926 mol aluminium will give :

$\frac{2}{2}\times 0.041926 mol=0.041926 mol$ of alum.

Mass of 0.041926 moles of alum:

0.041926 mol × 474 g/mol= 19.873 g

Theoretical yield of alum = 19.873 g

Percentage yield:

$\% Yield =\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Percentage yield of the alum:

$\% Yield =\frac{ 9.009 g}{19.873 g}\times 100=45.33\%$

The theoretical yield of alum is 19.873 grams and percent yield for this alum synthesis is 45.33%.

7 0

3 years ago