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2 years ago

Help on this question please

Chemistry

2 answers:

dedylja [7]2 years ago

5 0

Answer:

Choice 1: Position 3

Explanation:

The equinox is showed in Position 3 and 1.

Position 1 is fall, Position 2 is Winter, 3 is spring, 4 is summer. Since you are looking for the northern hemisphere, the shadowed area shown is position 2 is winter, spring is next in rotation so that already gives away the fact that position 3 is spring.

garri49 [273]2 years ago

4 0

Position 3 is the answer.

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Calculate the work, w, gained or lost by the system when a gas expands from 15 L to 45 L against a constant external pressure of

marta [7]

Answer:

Work done by the system = 4545 J

Explanation:

The expression for the calculation of work done is shown below as:

$w=-P\times \Delta V$

Where, P is the pressure

$\Delta V$ is the change in volume

From the question,

$\Delta V$ = 45 - 15 L = 30 L

P = 1.5 atm

$w=-1.5\times 30\ atmL$

Also, 1 atmL = 101 J

So,

$w=-1.0\times0.75\times 101\ J=-4545\ J$ (negative sign implies work is done by the system)

<u>Work done by the system = 4545 J</u>

6 0

3 years ago

There are two naturally occurring isotopes of boron. 10 B has a mass of 10.0129 u. 11 B has a mass of 11.0093 u. Determine the a

Vanyuwa [196]

<h2>Natural Abundance for 10B is 19.60%</h2>

Explanation:

The natural isotopic abundance of 10B is 19.60%.

The natural isotopic abundance of 11B is 80.40%.

The isotopic masses of boron are 10.0129 u and 11.009 u respectively.

For calculation of abundance of both the isotopes -

Supposing it was 50/50, the average mass would be 10.5, so to increase the mass we need a more percentage of 11.

Determining it as an equation -

10x + 11y= 10.8

x+y=1 (ratio)

10x + 10y = 10

By taking the denominator away from the numerator

we get;

y = 0.8

x + y = 1

∴ x = 0.2

To get percentages we need to multiply it by 100

So, the calculated abundance is 80% for 11 B and 20% 10 B.

5 0

3 years ago

How many moles of water are produced when 6.0 moles of hydrogen gas react with 2.5 moles of oxygen gas?

sasho [114]

Answer:

2.5 mole O2 should react (2 * 2.5) = 5.0 mole H2 but there is 6.0 mole H2. H2 remain in excess. O2 is the limiting reactant. mole of H2O formed = 2 * 2.5 = 5.0 mole.

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3 years ago

if 0.40 mol of h2 and .15 mol of o2 were to reat as completely as possible to produce h20, what mass of the reactant would remai

Sveta_85 [38]

Answer:

0.2g

Explanation:

Given parameters:

Number of moles of H₂ = 0.4mol

Number of moles of O₂ = 0.15mol

Unknown:

Mass of reactant that would remain = ?

Solution:

To solve this problem, we need to know the limiting reactant which is the one in short supply in the given reaction.

The expression of the reaction is :

2H₂ + O₂ → 2H₂O

2 mole of H₂ will combine with 1 mole of O₂

But given; 0.4 mole of H₂ we will require $\frac{0.4}{2}$ = 0.2mole of O₂

The given number of oxygen gas is 0.15mole and it is the limiting reactant.

Hydrogen gas is in excess;

1 mole of oxygen gas will combine with 2 mole of hydrogen gas

0.15 mole of oxygen gas will require 0.15 x 2 = 0.3mole of hydrogen gas

Now, the excess mole of hydrogen gas = 0.4 mole - 0.3 mole = 0.1mole

Mass of hydrogen gas = number of mole x molar mass

Molar mass of hydrogen gas = 2(1) = 2g/mol

Mass of hydrogen gas = 0.1 x 2 = 0.2g

8 0

2 years ago

Select the correct answer. Why does every chemical reaction require a certain amount of activation energy? A. Energy is released

horsena [70]

Answer:

<u>The answer is</u>: <em>B. </em><em>Energy lost to the environment during the reaction must be replaced.</em>

Explanation:

5 0

2 years ago