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3 years ago

7

Which of the following is an element? A. carbon monoxide gas (CO) B. magnesium chloride salt (MgCl) C. zinc metal (Zn) D. hydroc

hloric acid (HCl)

2 answers:

kolbaska11 [484]3 years ago

8 0

The answer is C. Zinc metal (Zn)

All of the other answers are compounds with multiple elements in them.

barxatty [35]3 years ago

6 0

The answer is C) zinc (Zn)

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Which of the following is a pure substance? Choose all that apply.

worty [1.4K]

Nickel is a pure substance

Rust is also a pure substance

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3 years ago

Read 2 more answers

In an electroplating process, copper (ionic charge +2e, atomic weight 63.6 g/mol) is deposited using a current of 10.0 A. What m

salantis [7]

Answer : The mass of copper deposit is, 1.98 grams

Explanation :

First we have to calculate the charge.

Formula used : $Q=I\times t$

where,

Q = charge = ?

I = current = 10 A

t = time = 10 min = 600 sec (1 min = 60 sec)

Now put all the given values in this formula, we get

$Q=10A\times 600s=6000C$

Now we have to calculate the number of atoms deposited.

As, 1 atom require charge to deposited = $2\times (1.6\times 10^{-19})$

Number of atoms deposited = $\frac{(6000)}{2\times(1.6\times 10^{-19})}=1.875\times 10^{22}$ atoms

Now we have to calculate the number of moles deposited.

Number of moles deposited = $\frac{(1.875\times 10^{22})}{(6.022\times 10^{23})}=0.03113$ moles

Now we have to calculate the mass of copper deposited.

1 mole of Copper has mass = 63.5 g

Mass of Copper Deposited = $63.5\times 0.03113 =1.98g$

Therefore, the mass of copper deposit is, 1.98 grams

5 0

3 years ago

A first-order decomposition reaction has a rate constant of 0.00440 yr−1. How long does it take for [reactant] to reach 12.5% of

mina [271]

Answer:

473 year

Explanation:

Using integrated rate law for first order kinetics as:

$[A_t]=[A_0]e^{-kt}$

Where,

$[A_t]$ is the concentration at time t

$[A_0]$ is the initial concentration

Given:

To reach 12.5% of reactant means that 0.125 of $[A_0]$ is decomposed. So,

$\frac {[A_t]}{[A_0]}$ = 0.125

t = ?

$\frac {[A_t]}{[A_0]}=e^{-k\times t}$

$0.125=e^{-0.00440\times t}$

t = 473 year

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3 years ago

Explain the working principle of a clinical thermometer

bagirrra123 [75]

Answer:

A clinical thermometer is a thermometer used to measure human body temperature. Most made in the 20th century are mercury-in-glass thermometers. They are accurate and sensitive, having a narrow place where the mercury level rises very fast. A kink in the tube stops the mercury level from falling on its own.

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3 years ago

Rank the following substances in order from most soluble in water to least soluble in water: methane, CH4; 2-butanol, C4H9OH; ma

inna [77]

Answer:

MgCl2 > C4H9OH > CH4 > C3H8.

Explanation:

Alkanes do not form hydrogen bonds and are insoluble in polar solvents e.g water. The hydrogen bonds between water molecules are move away from an alkane molecule and this worsens as their Carbon chain / molecular weight increases.

MgCl2 is soluble in water. Water essentially breaks down the ionic crystal lattice and the resulting solution is slightly basic.

Alcohols are generally soluble in water and this is because of the -OH group and its ability to form hydrogen bonds with water molecules. As applied to alkanes, as the carbon chain in the alkyl group increases, the solubility decreases.

From the most soluble to the least soluble,

MgCl2 > C4H9OH > CH4 > C3H8.

4 0

3 years ago