Explanation:
First, we need to calculate the number of moles of sodium carbonate we have in a 25 g sample. To calculate this, we will
find the molar mass of sodium carbonate (Na2CO3):
⇒ 2 × Molar mass of sodium + Molar mass of carbon + 3×molar mass of oxygen
⇒ 2 × 23 + 12 + 3 × 16
⇒ 46 + 12 + 48
⇒ 106g/mol
Thus, the molar mass of Na2CO3 is 106g/mol.
Therefore, number of moles = 25 ÷ 106
=> 0.2358 mol
Now, we know that every mole of Na2CO3 have 0.2358 moles of Na+ ions. Hence, total moles of Na2CO3 is 0.4716 moles
Number of ions present = 6.022 × 1023 × 0.4716 mol = 2.84 × 1023ions
Answer:
200g
Explanation:
Step 1:
The balanced equation for the reaction.
2Na + 2H2O —> 2NaOH + H2
Step 2:
Determination of the number of mole of NaOH produced by the reaction. This is illustrated below:
From the balanced equation above,
2 moles of H2O produced 2 moles of NaOH.
Therefore, 5 moles of H2O will also produce 5 moles of NaOH.
Step 3:
Conversion of 5 moles of NaOH to grams. This is illustrated below:
Number of mole of NaOH = 5 moles
Molar Mass of NaOH = 23 + 1 + 16 = 40g/mol
Mass of NaOH =?
Mass = number of mole x molar Mass
Mass of NaOH = 5 x 40
Mass of NaOH = 200g
Answer:
The correct statement is that the point of initial resistance is the level of depression that will fill the pipette with the desired volume of solution.
Explanation:
The pipette can be otherwise stored vertically or horizontally, this has nothing to do with the operation, and before the operation, the dial needs to be set. Also, the plastic pipette tip should not be ejected at all, thus, no new disposable plastic tip is required for each sample.
The correct statement is that the point of initial resistance is the level of depression that will fill the pipette with the desired volume of solution.
Answer:
38.7 g
Explanation:
first you find the molar mass of Nickle(II) Perchlorate
Nickle = 58.693 g/mol
Perchlorate is Chlorine and Oxygen combined
Molar mass of chlorine is 35.453 g/mol
Oxygen = 15.999 g/mol but since it has 4 oxygen atoms combined with chlorine you have to multiply 15.999 by 4 which is 63.996 add all the masses together and that gives you 158.142. Since you have moles you multiply the moles by the molar mass which looks like this. 0.245 * 158.142 which equals 38.74479 but with sign figs it is 38.7g as your final answer. Ask me if you are confused about something.
Answer:
B
Explanation:
The ratios of the coefficient of the compounds in a balanced chemical equation tells us the relationship of each compound to the others in terms of mole.
Based on the equation,
3 moles of CO₂ would require 2 moles of phosphoric acid.
3 mol CO₂ ------- 2 mol H₃PO₄
1.5 mol CO₂ ------- 2 ÷2= 1 mol H₃PO₄
Or 1.5 mol would require 
mol of H₃PO₄
To find mass of H₃PO₄, multiply the number of moles by its Mr, which can be deduced with the help of the periodic table.
Ar of H₃PO₄
= 3(Ar of H) + Ar of P +4(Ar of O)
= 3(1) +31 +4(16)
= 98
Multiply 98 with the number of moles, 1, to obtain the answer.
So if you would look at the steps above, here's what we did:
