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3 years ago

Which of these elements has the lowest melting point? (1) Li (3) K (2) Na (4) Rb

2 answers:

4 0

The answer is (4) Rb. From observation, we can find that these four elements are from first column. The melting point from top to the bottom is from high to low. So the answer is (4).

natali 33 [55]3 years ago

4 0

Answer: Option (4) is the correct answer.

Explanation:

It is known that on moving down a group there will be decrease in melting point of the element because of increase in number of shells.

As a result, outermost electrons move away from the nucleus due to which there will be decrease in force of attraction between the protons and valence electrons. Hence, there will be decrease in melting point.

Therefore, the given elements are of same group and Rb has largest atomic size.

Thus, we can conclude that Rb has the lowest melting point.

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What is the correct name for Mn(NO3),

kupik [55]

Answer:

Manganese trinitrate or manganese(III) nitrate

Explanation:

6 0

3 years ago

In the past earths sea level has sometimes been lower at that time which of the following would have been a major difference in

valina [46]

The answer which would have been a major difference in the ocean basins is the following one:
B. Mid-ocean ridges would have been chains of mountains.

Given that the waters were lower in the past, those ridges would no longer be just mid-ocean ridges, but complete mountains due to the low levels of water around them.

8 0

3 years ago

Read 2 more answers

Consider the reaction:

murzikaleks [220]

Answer: The formation of given amount of oxygen gas results in the absorption of 713 kJ of heat.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of oxygen gas = 83 g

Molar mass of oxygen gas = 32 g/mol

Putting values in above equation, we get:

$\text{Moles of oxygen gas}=\frac{83g}{32g/mol}=2.594mol$

For the given chemical equation:

$2Fe_2O_3\rightarrow 4Fe+3O_2;\Delta H^o_{rxn}=+824.2kJ$

Sign convention of heat:

When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.

By Stoichiometry of the reaction:

When 3 moles of oxygen gas is formed, the amount of heat absorbed is 824.2 kJ

So, when 2.594 moles of oxygen gas is formed, the amount of heat absorbed will be = $\frac{824.2kJ}{3mol}\times 2.59mol=713kJ$

Hence, the formation of given amount of oxygen gas results in the absorption of 713 kJ of heat.

7 0

3 years ago

What if you broke off a piece of cement (or bread) so that it was only half the volume of the original piece? What would happen

MAVERICK [17]

Answer:

The mass is also half of the mass of the original piece

Explanation:

Recall that the volume of a substance is defined as mass/volume. The density of substances is a constant. Hence, if a break off a piece of cement or bread such that what remains is only half the volume of the original piece, the mass of the new piece must also reduce to half of the mass of the original piece so that the volume of the material will remain constant.

Hence the answer above.

4 0

3 years ago

A piece of Li is

Solnce55 [7]

It’s a chemical change

8 0

2 years ago