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3 years ago

Which is a sign of a chemical change?

Chemistry

1 answer:

Igoryamba3 years ago

7 0

The correct answer for the question it is option

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Purification of nickel can be achieved by electrorefining nickel from an impure nickel anode onto a pure nickel cathode in an el

Alexxandr [17]

Answer: 530 hours

Explanation:

The reduction of Nickel ions to nickel is shown as:

$Ni^{2+}+2e^-\rightarrow Ni$

$96500\times 2=193000Coloumb$ of electricity deposits 1 mole of Nickel

1 mole of Nickel weighs = 58.7 g

Given quantity = 18.0 kg = 18000 g (1kg=1000g)

58.7 g of Nickel is deposited by 193000 C of electricity

18000 g of Nickel is deposited by = $\frac{193000}{58.7}\times 18000=59182282.8C$ of electricity

$Q=I\times t$

where Q= quantity of electricity in coloumbs = 59182282.8C

I = current in amperes = 31.0 A

t= time in seconds = ?

$59182282.8C=31.0A\times t$

$t=1909105.9sec$

(1h=3600 sec)

$t=530hours$

Thus 530 hours are required to plate 18.0 kg of nickel onto the cathode if the current passed through the cell is held constant at 31.0 A

3 0

3 years ago

If the atomic weight of nitrogen is 14.01, what is the mass of the nitrogen atoms in one mole of cadmium nitrate, Cd(NOÀ)

Nadya [2.5K]

The answer is 28.02.

The chemical formula for cadmium nitrate is Cd(NO₃)₂.

There are in total 2 nitrogen atoms in Cd(NO₃)₂. If <span>the atomic weight of nitrogen is 14.01</span>, the mass <span>of two nitrogen atoms in one mole of cadmium nitrate is 28.02:
2 </span>· 14.01 = 28.02

8 0

3 years ago

If you live in the southern hemisphere, what season would you be experiencing in position C this diagram?

lisabon 2012 [21]

The answer is spring it would be fall in the north and spring in the south

7 0

3 years ago

Read 2 more answers

Information gathered by a scientist about the toxicity of chemical X and chemical Y showed that they had individual safe limits

timofeeve [1]

Answer:

Synergism

Explanation:

This is an example of Synergism. Synergism is nothing but working out of two medicines together.

Examples of medical synergies are when doctors treat microbial heart infections with ampicillin and Gentamicin and when people with cancer undergo radiation and chemotherapy or more than one chemotherapy drug at a time.

6 0

3 years ago

What is the oxidation number of cl− in the hypochlorite ion clo−?

mariarad [96]

Answer : The oxidation number of chlorine (Cl) is, (+1)

Explanation :

Oxidation number : It represent the number of electrons lost or gained by the atoms of an element in a compound.

Oxidation numbers are generally written with the sign (+) and (-) first and then the magnitude.

When the atoms are present in their elemental state then the oxidation number will be zero.

Rules for Oxidation Numbers :

The oxidation number of a free element is always zero.

The oxidation number of a monatomic ion equals the charge of the ion.

The oxidation number of Hydrogen (H) is +1, but it is -1 in when combined with less electronegative elements.

The oxidation number of oxygen (O) in compounds is usually -2, but it is -1 in peroxides.

The oxidation number of a Group 1 element in a compound is +1.

The oxidation number of a Group 2 element in a compound is +2.

The oxidation number of a Group 17 element in a binary compound is -1.

The sum of the oxidation numbers of all of the atoms in a neutral compound is zero.

The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion.

The given compound is, $ClO^-$

Let the oxidation state of 'Cl' be, 'x'

$x+(-2)=-1\\\\x-2=-1\\\\x=+1$

Therefore, the oxidation number of chlorine (Cl) is, (+1)

5 0

3 years ago