All categories

3 years ago

Which statement describes the periodic table?

Chemistry

1 answer:

Lorico [155]3 years ago

5 0

Answer:

The periodic table is a tabular array of the chemical elements organized by atomic number, from the element with the lowest atomic number, hydrogen, to the element with the highest atomic number, oganesson. The atomic number of an element is the number of protons in the nucleus of an atom of that element.

You might be interested in

You are given three beakers of unknown liquids. One beaker contains sugar water. Without tasting the liquids, how could you iden

Marrrta [24]

You would observe, trying to identify if there's a minimum difference in each beaker. Like, colour, or using an bagueta (idk how to say it in english), churning it or something like that.

8 0

3 years ago

Using a molar heat of combustion of hexane (C6H14) –4163 kJ/mol, the mass of hexane required to increase the temperature of 1.76

pshichka [43]

Answer:

7.46 g.

Explanation:

Firstly, we need to calculate the amount of heat needed to warm 5.64 kg of water from 21.0°C to 70.0°C using the relation:

Q = m.c.ΔT,

where, Q is the amount of heat absorbed by water (Q = ??? J).

m is the mass of water (m: we will determine).

c is the specific heat capacity of water (c = 4.186 J/g.°C).

ΔT is the temperature difference (final T - initial T) (ΔT = 70.0 °C - 21.0 °C = 49.0 °C).

To determine the mass of 1.76 L of water we can use the relation:

mass = density x volume.

density of water = 1000 g/L & V = 1.76 L.

∴ mass = density x volume = (1000 g/L)(1.76 L) = 1760.0 g.

∵ Q = m.c.ΔT

∴ Q = m.c.ΔT = (1760.0 g)(4.186 J/g.°C)(49.0 °C) = 360483.2 J ≅ 360.4832 kJ.

As mentioned in the problem the molar heat of combustion of hexane is - 4163.0 kJ/mol.

Using cross multiplication we can get the no. of moles of hexane that are needed to be burned to release 360.4832 kJ:

Combustion of 1.0 mole of methane releases → - 4163.0 kJ.

Combustion of ??? mole of methane releases → - 360.4832 kJ.

∴ The no. of moles of hexane that are needed to be burned to release 360.4832 kJ = (- 360.4832 kJ)(1.0 mol)/(- 4163.0 kJ) = 0.0866 mol.

Now, we can get the mass of hexane that must be burned to warm 1.76 L of water from 21.0°C to 70.0°C:

∴ mass = (no. of moles needed)(molar mass of hexane) = (0.0866 mol)(86.18 g/mol) = 7.46 g.

5 0

3 years ago

Pls help me with is question.

Dennis_Churaev [7]

Answer:

25cm³ = 0.025L of H2So4

Molarity of H2SO4 = 1moldm-³

Recall ... 1dm-³ = 1L

So the Molarity can also be 1mol/L

Mole = Molarity x volume in L

Mole of H2SO4 = 1mol/L x 0.025L

=0.025Moles of Sulphuric acid reacted.

From the equation of reaction

1mole of H2SO4 reacts to produce 1mole of Copper sulphate crystal

Since their Mole ratio is 1:1

It means that Since 0.025mole of H2SO4 reacted.... 0.025mole of CuSO4.5H2O would be produced

Nice.. OK

So we know the moles of CuSO4.5H2O produced

We can get the Mass

Recall

From

Mole=Mass/Molar Mass

Mass = Mole x Molar Mass

Molar Mass of CuSO4.5H2O = 64 + 32 + 16x4+ 5(2+16)

Mm= 250g/mol

Mass = 0.025mol x 250g/mol

= 6.25g of CuSO4.5H2O crystals Would be PRODUCED.

5 0

3 years ago

Find the enthalpy of neutralization of HCl and NaOH. 87 cm3 of 1.6 mol dm-3 hydrochloric acid was neutralized by 87 cm3 of 1.6 m

Vesna [10]

Answer : The correct option is, (A) -101.37 KJ

Explanation :

First we have to calculate the moles of HCl and NaOH.

$\text{Moles of HCl}=\text{Concentration of HCl}\times \text{Volume of solution}=1.6mole/L\times 0.087L=0.1392mole$

$\text{Moles of NaOH}=\text{Concentration of NaOH}\times \text{Volume of solution}=1.6mole/L\times 0.087L=0.1392mole$

The balanced chemical reaction will be,

$HCl+NaOH\rightarrow NaCl+H_2O$

From the balanced reaction we conclude that,

As, 1 mole of HCl neutralizes by 1 mole of NaOH

So, 0.1392 mole of HCl neutralizes by 0.1392 mole of NaOH

Thus, the number of neutralized moles = 0.1392 mole

Now we have to calculate the mass of water.

As we know that the density of water is 1 g/ml. So, the mass of water will be:

The volume of water = $87ml+87ml=174ml$

$\text{Mass of water}=\text{Density of water}\times \text{Volume of water}=1g/ml\times 174ml=174g$

Now we have to calculate the heat absorbed during the reaction.

$q=m\times c\times (T_{final}-T_{initial})$

where,

q = heat absorbed = ?

$c$ = specific heat of water = $4.18J/g^oC$

m = mass of water = 174 g

$T_{final}$ = final temperature of water = 317.4 K

$T_{initial}$ = initial temperature of metal = 298 K

Now put all the given values in the above formula, we get:

$q=174g\times 4.18J/g^oC\times (317.4-298)K$

$q=14110.008J=14.11KJ$

Thus, the heat released during the neutralization = -14.11 KJ

Now we have to calculate the enthalpy of neutralization.

$\Delta H=\frac{q}{n}$

where,

$\Delta H$ = enthalpy of neutralization = ?

q = heat released = -14.11 KJ

n = number of moles used in neutralization = 0.1392 mole

$\Delta H=\frac{-14.11KJ}{0.1392mole}=-101.37KJ/mole$

Therefore, the enthalpy of neutralization is, -101.37 KJ

3 0

3 years ago

What is the systematic name for the following structure, specifying cis-/trans-?

Andrej [43]

Answer:

cis-3,4-dimethyl-3-hexene

Explanation: since the substituents are on same side, it call cis. Followed by the name

6 0

3 years ago