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3 years ago

Which is the last thing to be seen before a total eclipse?

1 answer:

8 0

<span>When the Moon has nearly blocked out the sun at the last few minutes before the total solar eclipse, you will see some points of light surrounding the edges of the dark Moon. These look like a string of beads wrapped around the edges and are appropriately called Baily's Beads. They are named after the astronomer Francis Baily who first noticed them in the 18th century. These beads only appear for a few brief minutes before the total solar eclipse occurs.</span>

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Dissolving 5.28 g of an impure sample of calcium carbonate in hydrochloric acid produced 1.14 L of carbon dioxide at 20.0 °C and

swat32

Answer:

$\%\ mass\ of\ CaCO_3=93.37\ \%$

Explanation:

Given that:

Pressure = 791 mmHg

Temperature = 20.0°C

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15

So,

T = (20 + 273.15) K = 293.15 K

T = 293.15 K

Volume = 100 L

Using ideal gas equation as:

PV=nRT

where,

P is the pressure

V is the volume

n is the number of moles

T is the temperature

R is Gas constant having value = 62.3637 L.mmHg/K.mol

Applying the equation as:

791 mmHg × 1.14 L = n × 62.3637 L.mmHg/K.mol × 293.15 K

⇒n of $CO_2$ produced = 0.0493 moles

According to the reaction:-

$CaCO_3 + 2 HCl\rightarrow CaCl_2 + H_2O + CO_2$

1 mole of carbon dioxide is produced 1 mole of calcium carbonate reacts

0.0493 mole of carbon dioxide is produced 0.0493 mole of calcium carbonate reacts

Moles of calcium carbonate reacted = 0.0493 moles

Molar mass of $CaCO_3$ = 100.0869 g/mol

The formula for the calculation of moles is shown below:

$moles = \frac{Mass\ taken}{Molar\ mass}$

Thus,

$0.0493\ mol= \frac{Mass}{100.0869\ g/mol}$

$Mass_{CaCO_3}=4.93\ g$

Impure sample mass = 5.28 g

Percent mass is percentage by the mass of the compound present in the sample.

$\%\ mass\ of\ CaCO_3=\frac{Mass_{CaCO_3}}{Total\ mass}\times 100$

$\%\ mass\ of\ CaCO_3=\frac{4.93}{5.28}\times 100$

$\%\ mass\ of\ CaCO_3=93.37\ \%$

3 0

3 years ago

If a given aqueous solution at 298 K contains [H+] = 1.0 × 10-9, what is the [OH-]?

Zinaida [17]

Answer:

Explanation:

$\frac{1x10}x^{-14} = 1x10^{-9} \\ x =1x10^{-5} \\\\[OH][H]= 1x10^{-14}$

The concetration can be found by dividing the water ph constant by the [H=] or [OH] to find the other

6 0

3 years ago

a 108ml sampl of gas has a mass of 77.96mg at a pressure of 1140mmhg and temperature of 183°c .what is the molar mass of the gas

madam [21]

Answer:

146.85 g/mol

Explanation:

PV=nRT

n=mass/molar mass

covert from mmhg to atm = 0.184 atm

convert from ml to L= 0.108 L

convert from degree C to K= 456.15 K

convert from mg to g= 0.07796g

then rearrange the formula:

n=PV/RT

=(0.184)(0.108)/(0.08206)(456.15)

n= 5.308*10^(-4)

rearrange the n formula interms of molar mass:

Molar mass= mass/n

=0.07796/(5.308*10^-4)

molar mass= 146.85g/mol

3 0

3 years ago

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In an isolated system:

ipn [44]

Answer:

isolated system (plural isolated systems) (physics) A system that does not interact with its surroundings. Depending on context this may mean that its total energy and/or momentum stay constant.

Explanation:

An isolated system is a thermodynamic system that cannot exchange either energy or matter outside the boundaries of the system. ... The system may be enclosed such that neither energy nor mass may enter or exit.

is there both?

7 0

3 years ago

What did Thomson’s model of the atom include that Dalton’s model did not have?

Allushta [10]

Thomson's model included Protons and Electrons. His model is referred to as 'Plum Pudding' because of it.

6 0

3 years ago

Read 2 more answers