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lukranit [14]
1 year ago
15

Scientific method practice hypothesis construction & experimental design

Chemistry
1 answer:
Gelneren [198K]1 year ago
3 0
A supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation
You might be interested in
Hard water often contains dissolved Ca2+ and Mg2+ ions. One way to soften water is to add phosphates. The phosphate ion forms in
avanturin [10]
<span>5.5×10−2M in calcium chloride and 8.0×10−2M in magnesium nitrate.
What mass of sodium phosphate must be added to 1.5L of this solution to completely eliminate the hard water ion

1) Content of Ca (2+) ions

Calcium chloride = CaCl2

Ionization equation: CaCl2 ---> Ca (2+) + 2 Cl (-)

=> Molar ratios: 1 mol of CaCl2 : 1 mol Ca(2+) : 2 mol Cl(-)

Calculate the number of moles of CaCl2 in 1.5 liters of 5.5 * 10^-2 M solution

M = n / V => n = M*V = 5.5 * 10^ -2 M * 1.5 l = 0.0825 mol CaCl2

=> 0.0825 mol Ca(2+)

2) Number of phosphate ions needed to react with 0.0825 mol Ca(2+)

formula of phospahte ion: PO4 (3-)

molar ratio: 2PO4(3-) + 3Ca(2+) = Ca3 (PO4)2

Proportion: 2 mol PO4(3-) / 3 mol Ca(2+) = x / 0.0825 mol Ca(2+)

=> x = 0.0825 coml Ca(2+) * 2 mol PO4(3-) / 3 mol Ca(2+) = 0.055 mol PO4(3-)

3) Content of Mg(2+) ions

Ionization equation: Mg (NO3)2 ----> Mg(2+) + 2 NO3 (-)

Molar ratios: 1 mol Mg(NO3)2 : 1 mol Mg(2+) + 2 mol NO3(-)

number of moles of Mg(NO3)2 in 1.5 liter of 8.0 * 10^-2 M solution

n = M * V = 8.0 * 10^ -2 M * 1.5 liter = 0.12 moles Mg(NO3)2

ions of Mg(2+) = 0.12 mol Mg(NO3)2 * 1 mol Mg(2+) / mol Mg(NO3)2 = 0.12 mol Mg(2+)

4) Number of phosphate ions needed to react with 0.12 mol Mg(2+)

2PO4(3-) + 3Mg(2+) = Mg3(PO4)2

=> 2 mol PO4(3-) / 3 mol Mg(2+) = x / 0.12 mol Mg(2+)

=> x = 0.12 * 2/3 mol PO4(3-) = 0.16 mol PO4(3-)

5) Total number of moles of PO4(3-)

0.055 mol + 0.16 mol = 0.215 mol

6) Sodium phosphate

Sodium phosphate = Na3(PO4)

Na3PO4 ---> 3Na(+) + PO4(3-)

=> 1 mol Na3PO4 : 1 mol PO4(3-)

=> 0.215 mol PO4(3-) : 0.215 mol Na3PO4

mass in grams = number of moles * molar mass

molar mass of Na3 PO4 = 3*23 g/mol + 31 g/mol + 4*16 g/mol = 164 g/mol

=> mass in grams = 0.215 mol * 164 g/mol = 35.26 g

Answer: 35.26 g of sodium phosphate
</span>
5 0
4 years ago
Circle only those of the following reactions that are redox reactions:
Citrus2011 [14]

Answer: options B,D and F

Explanation:

Since redox reactions are those which involves both oxidation and reduction

In B , Cu is oxidized and S gets reduced

D, Na gets oxidized and hydrogen gets reduced

F, carbon gets oxidized and Oxygen gets reduced

In g, there is no change in oxidation no of s in both product and Reactants is same +4

Similarly in the case of Ag and Mg.

5 0
3 years ago
Paano napaunlad ng mga Latin ang Rome at ano ang natulong ng mga Etruscan sa kanila?​
Hitman42 [59]

Answer:

yesakskakakakakakkawbajajjakaak

7 0
3 years ago
Which of the following is mixture backi g soda or carbon or honey or orange juice
vfiekz [6]

Answer:

Honey

Explanation:

Backing soda:

Backing soda is a compound that is made up of only one kind of salt called NaHCO3 or sodium  hydrogen carbonate. All the molecules  of NaHCO3  are identical and we know that a mixture is something made up of two or more than two kinds of things, therefore baking soda cannot be referred to as mixture.

Carbon:

Carbon is not a mixture because its just an element that composed diffreent compounds by reacting with different other elements. In its oure form carbon is not a mixture, but if it is combined with some other substance it can form mixture.

Orange juice:

It depends on what kind of orange juice we are talking about. If we are talking about pure orange juice that is made from fresh oranges,then no - it cannot be called as mixture. However, if sugars,flavors and other preservatives are added like those available in market then it can be a mixture.

Honey:

Honey is a mixture of at-least 181 types of components in which most of all are sugars. These components mix through complex process and give the honey its specific sugary taste. You can see some of the constituent components of honey in attached figure.

Hope it help!


5 0
4 years ago
19) What is the molarity of a KOH solution if 200 ml of the solution contains 0.6 moles KOH?
zloy xaker [14]

Answer: 3M

Explanation: Molarity : It is defined as the number of moles of solute present in one liter of solution.

Formula used :

Molarity=\frac{n\times 1000}{V_s}

where,

n = moles of solute KOH = 0.6 moles

V_s = volume of solution in ml= 200 ml

Now put all the given values in the formula of molarity, we get

Molarity=\frac{0.6moles\times 1000}{200ml}=3mole/L

Therefore, the molarity of solution will be 3M.

8 0
3 years ago
Read 2 more answers
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