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Stella [2.4K]
3 years ago
12

A 5.0-gram sample of zinc and a 50.-milliliter sample of hydrochloric acid are used in a chemical reaction. Which combination of

these samples has the fastest reaction rate?
(1) a zinc strip and 1.0 M HCl(aq)
(2) a zinc strip and 3.0 M HCl(aq)
(3) zinc powder and 1.0 M HCl(aq)
(4) zinc powder and 3.0 M HCl(aq)
Chemistry
2 answers:
Radda [10]3 years ago
7 0
The answer is Zine powder and 3.0 M HCl (aq)
inessss [21]3 years ago
5 0

Answer:

(4) zinc powder and 3.0 M HCl(aq)

Explanation:

First consider the equation of reaction:

Zn + 2HCl --> ZnCl_2 + H_2

1 mole of Zinc requires 2 moles of HCl for reaction.

mole of zinc = mass/molar mass = 5.0/65.38 = 0.0765 mole

0.0765 mole of zinc will require: 0.0765 x 2 = 0.1530 mole HCl

Mole of 1.0 M HCl = Molarity x volume = 1 x 0.05 = 0.05 mole

Mole of 3.0 M HCl = 3 x 0.05 = 0.15

Hence, the 3.0 M HCl is what will give the required number of mole.

<em>Zinc in powder form will react faster compared to in strip because the former has higher surface area for reaction.</em>

Therefore, zinc powder and 3.0 M HCl will give the fastest reaction rate.

<em>The correct option is option 4.</em>

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A helium balloon is filled on the ground where the atmospheric pressure is 768 torr. The volume of the balloon is 8.00 m3. When
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Answer:

The correct option is: <u>B. 366 torr</u>

Explanation:

Given: <u>On the ground</u>- Initial Volume: V₁ = 8.00 m³, Initial Atmospheric Pressure: P₁= 768 torr;

<u>At 4200 m height</u>- Final Volume: V₂ = 16.80 m³, Final Atmospheric Pressure: P₂ = ?

Amount of gas: n, and Temperature: T = constant

<u>According to the Boyle's Law</u>, for a given amount of gas at constant temperature:         P₁ V₁ = P₂ V₂

⇒  P₂ = P₁ V₁ ÷ V₂

⇒  P₂ = [(768 torr) × (8.00 m³)] ÷ (16.80 m³)

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6 0
3 years ago
Kinetic energy and gravitational potential energy are both forms of which type
scoundrel [369]

Answer:

<em>C. Potential energy</em>

Explanation:

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The vapor pressure of water at 25.0°c is 23.8 torr. determine the mass of glucose (molar mass = 180 g/mol) needed to add to 500.
svp [43]
Q: A
according to this formula, we can get the mole fraction of water (n):
P(solu) = n Pv(water)
when we have Pv(solu) = 22.8 and Pv(water) = 23.8 so by substitution:
22.8 = n * 23.8
n= 0.958
- we need to get the moles of glucose:
moles of water = 500 g(mass weight) / 18 (molar weight)= 27.7 mol
n = moles of water / ( moles of water + moles of glucose)
0.958   = 27.7 / ( 27.7+ moles of glucose)
0.958 moles of glucose + 26.5 = 27.7
0.968 moles of glucose = 1.2
moles of glucose = 1.253 mol
∴ the mass of glucose = no.of glucose moles x molar mass 
                                      = 1.253 x 180 = 225.5 g
Q: B
here we also need to get n (mole fraction of water )by using this formula:
Pv(solu) = n Pv(water)
when we have Pv(solu)=132 & Pv(water)=150 so, by substition:
132= n * 150
n = 0.88
so, mole fraction of solution = 1 - 0.88 = 0.12
and we can get after that the moles of water = (mass weight / molar mass)
- no.moles of water = 85 g / 18 g/mol = 4.7 moles
- total moles in solution = moles of water / moles fraction of water 
                                        = 4.7 / 0.88 = 5.34 moles 
∴ moles of the solution = total moles in solu - moles of water 
                                       = 5.34 - 4.7 = 0.64 moles solute
∴ the molar mass of the solute = mass weight of solute / no.of moles of solute
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Q: C

moles of urea (NH2)2 CO = mass weight / molar mass
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moles of methanol = mass weight / molar mass 
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by substitution in Pv formula we will be able to get the vapour pressure of the solu :
Pv(solu) = n P°v
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