Which planet listed below will take the longest amount of time to orbit the sun?

Which of the following represents positron emission? Select one: a. 3015P ---> 3014Si + ___ b. 23892U ---> 23490Th + ___ c

xxTIMURxx [149]

The simple trick which one can consider in such problem where it is asked for positron emission is :
When the atomic number goes DOWN by one and mass number remains unchanged, then a positron is emitted.

a. $P^{30}_{15} ----\ \textgreater \ Si^{30}_{14} + e^{0}_{1}^+$

Here the atomic number decreases by one.

Similarly, options b and d are eliminated.

Option c is also not the answer.
For c, Count the atomic number on left side and compare it with right side. You will see it is 9 on left and 8 on right. Atomic no. did go down by 1. But the atomic mass is changed as well.

8 0

3 years ago

What is the difference between the molar mass and the empirical formula mass of a compound? when are these masses the same, and

fomenos

Molar mass is the mass of one stable molecule of a compound, that cannot join with another molecule of the same kind to form a new one, while an empirical formula is the molecular formula in its simplest form. E.g. empirical formula of ethene is CH2while its molecular formula is C2H4.

8 0

3 years ago

You use 4.98 g of Na2SO4, how many grams of barium sulfate are produced? Na2+Ba(NO3)2= ?

Kaylis [27]

Answer:

Mass of barium sulfate = 8.17 g

Explanation:

Given data:

Mass of sodium sulfate = 4.98 g

Mass of barium sulfate produced = ?

Solution:

Na₂SO₄ + Ba(NO₃)₂ → BaSO₄ + 2NaNO₃

Moles of sodium sulfate:

Number of moles = mass/molar mass

Number of moles =4.98 g / 142.04 g/mol

Number of moles = 0.035 mol

Now we will compare the moles pf sodium sulfate and with barium sulfate.

Na₂SO₄ : BaSO₄

1 : 1

0.035 : 0.035

Mass of barium sulfate:

Mass = number of moles × molar mass

Mass = 0.035 mol ×233.4 g/mol

Mass = 8.17 g

6 0

3 years ago

What is the correct definition of energy?

scoray [572]

Answer:

The ability to do work

Explanation:

Energy refers to the ability to carry out work.
It is measured in Joules (J).
Energy may exist in different forms such as potential energy when a body is at rest, kinetic energy when the body is in motion, etc.
Energy can neither be created nor destroyed, however, it can be transformed from one form to another. For example, chemical energy may be transformed into mechanical energy or other forms of energy.

6 0

3 years ago

Read 2 more answers

Cryolite, Na3AlF6(s), an ore used in the production of aluminum, can be synthesized using aluminum oxide. Balance the equation f

dmitriy555 [2]

Answer: The mass of cryolite produced is 51.48 kg

Explanation:

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

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

For aluminium oxide:

Given mass of aluminium oxide = 12.5 kg = 12500 g (Conversion factor: 1 kg = 1000 g)

Molar mass of aluminium oxide = 101.96 g/mol

Putting values in equation 1, we get:

$\text{Moles of aluminium oxide}=\frac{12500g}{101.96g/mol}=122.6mol$

For NaOH:

Given mass of NaOH = 55.4 kg = 55400 g

Molar mass of NaOH = 40 g/mol

Putting values in equation 1, we get:

$\text{Moles of NaOH}=\frac{55400g}{40g/mol}=1389mol$

For HF:

Given mass of HF = 55.4 kg = 55400 g

Molar mass of HF = 20 g/mol

Putting values in equation 1, we get:

$\text{Moles of HF}=\frac{55400g}{20g/mol}=2770mol$

For the given chemical reaction:

$Al_2O_3(s)+6NaOH(l)+12HF(g)\rightarrow 2Na_3AlF_6+9H_2O(g)$

By Stoichiometry of the reaction:

1 mole of aluminium oxide reacts with 6 moles of sodium hydroxide and 12 moles of HF.

So, 122.6 moles of aluminium oxide will react with $(6\times 122.6)=735.6mol$ of sodium hydroxide and $(12\times 122.6)=1471.2mol$ of HF

As, given amount of NaOH and HF is more than the required amount. So, they are considered as an excess reagent.

Thus, aluminium oxide is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

1 mole of aluminium oxide produces 2 moles of cryolite

So, 122.6 moles of aluminium oxide will produce = $\frac{2}{1}\times 122.6=245.2mol$ of cryolite

Now, calculating the mass of cryolite by using equation 1:

Molar mass of cryolite = 209.94 g/mol

Moles of cryolite = 245.2 mol

Putting values in equation 1, we get:

$245.2mol=\frac{\text{Mass of cryolite}}{209.94g/mol}\\\\\text{Mass of cryolite}=(245.2mol\times 209.94g/mol)=51477.3g$

Converting this into kilograms, we use the conversion factor:

1 kg = 1000 g

So, $51477.3 g\times (\frac{1kg}{1000g})=51.48kg$

Hence, the mass of cryolite produced is 51.48 kg

7 0

3 years ago