Please help not trying to fail this year

Which two practices are examples of how people use science?

Anika [276]

B. Developing theories using many lines of evidence

4 0

3 years ago

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Which tool was most likely used in a procedure if the lab report shows that approximately 300 mL of water was used ?

Travka [436]

Graduated Cylinder is the answer to this.

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What is true of neutrons? They have no charge and are located inside the nucleus. They have no charge and are located outside th

Inessa [10]

They have no charge and are located inside the nucleus

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3 years ago

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Write the balanced chemical equation for the neutralization reaction that occurs when an aqueous solution of hydrochloric acid (

Vladimir79 [104]

Answer:

HCl(aq) + KOH(aq) —> KCl(aq) + H2O(l)

Explanation:

Aqueous solution of HCl and aqueous solution of KOH react as follow:

HCl(aq) + KOH(aq) —>

In solution, HCl and KOH will dissociates as follow:

HCl —> H+ + Cl-

KOH —> K+ + OH-

During the reaction, a double displacement reaction occur as shown below:

H+ + Cl- + K+ + OH- —> K+Cl- + H+OH-

The elemental equation is given below:

HCl(aq) + KOH(aq) —> KCl(aq) + H2O(l)

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3 years ago

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1. Tooth enamel consists mainly of hydroxyapatite (Ca5(PO4)3(OH). When tin(II)fluoride is added to toothpaste it reacts with the

Sliva [168]

<u>Answer:</u> The mass of hydroxyapatite that can be converted is 0.733 grams

<u>Explanation:</u>

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

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

Given mass of tin(II)fluoride = 0.115 g

Molar mass of tin(II)fluoride = 156.7 g/mol

Putting values in equation 1, we get:

$\text{Moles of tin(II)fluoride}=\frac{0.115g}{156.7g/mol}=0.00073mol$

The chemical equation for the reaction of tin(II)fluoride and hydroxyapatite follows:

$SnF_2+2Ca_5(PO_4)_3(OH)\rightarrow 2Ca_5(PO_4)_3F+SnO+H_2O$

By Stoichiometry of the reaction:

1 mole of tin (II) fluoride reacts with 2 moles of hydroxyapatite

So, 0.00073 moles of tin (II) fluoride will react with = $\frac{2}{1}\times 0.00073=0.00146mol$ of hydroxyapatite

Now, calculating the mass of hydroxyapatite by using equation 1, we get:

Moles of hydroxyapatite = 0.00146 moles

Molar mass of hydroxyapatite = 502.3 g/mol

Putting values in equation 1, we get:

$0.00146mol=\frac{\text{Mass of hydroxyapatite}}{502.3g/mol}\\\\\text{Mass of hydroxyapatite}=(0.00146mol\times 502.3g/mol)=0.733g$

Hence, the mass of hydroxyapatite that can be converted is 0.733 grams

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3 years ago