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2 years ago

The law of conservation in mass

1 answer:

8 0

The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. ... If we account for all reactants and products in a chemical reaction, the total mass will be the same at any point in time in any closed system.

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What is the half-life of a 12 g sample of radioisotope that decayed to 6 g in 28

Charra [1.4K]

Answer:

A. 28 years

Explanation:

Applying,

R = R'(2ᵃ/ⁿ).............. Equation 1

Where R = Original sample, R' = Sample left after decay, a = Total time taken to decay, n = half life.

From the question,

Given: R = 12 g, R' = 6 g, a = 28 years.

Substitute into equation 1 and solve for n

12 = 6(2²⁸/ⁿ)

12/6 = 2²⁸/ⁿ

2²⁸/ⁿ = 2

Equation the base,

28/n = 1

n = 28 years.

Hence the half-life is 28 years

4 0

3 years ago

Which is the correct net ionic equation for the following reaction: H3PO4 (aq) + 3 LiOH (aq) > Li3PO4 (aq) + 3 H2O (l)?

torisob [31]

Answer: The correct option for the chemical equation $H_3PO_4(aq.)+3LiOH(aq.)\rightarrow Li_3PO_4(aq.)+3H_2O(l)$ is 1.

The correct option for the chemical equation $2HBr(aq.)+Co(OH)_2(aq.)\rightarrow CoBr_2(aq.)+2H_2O(l)$ is 3.

Explanation:

For the chemical equation:

$H_3PO_4(aq.)+3LiOH(aq.)\rightarrow Li_3PO_4(aq.)+3H_2O(l)$

$H_3PO_4$ is a weak acid and hence will not dissociate into ions whereas LiOH is a strong base and will easily dissociate into ions.

The product $Li_3PO_4$ is soluble in water and hence, will dissociate into its respective ions. Hence, the ionic equation for this reaction is:

$H_3PO_4(aq.)+3Li^{3+}(aq.)+3OH^-(aq.)\rightarrow 3Li^{3+}(aq.)+PO_4^{3-}(aq.)+3H_2O(l)$

Net ionic equation becomes:

$H_3PO_4(aq.)+3OH^-(aq.)\rightarrow PO_4^{3-}(aq.)+3H_2O(l)$

So, the correct option is 1.

For the chemical equation:

$2HBr(aq.)+Co(OH)_2(aq.)\rightarrow CoBr_2(aq.)+2H_2O(l)$

HBr and $Co(OH)_2$ are strong acid and strong base respectively, hence they will easily dissociate into ions.

The product, $CoBr_2$ is is soluble in water and hence, will dissociate into its respective ions. Hence, the ionic equation for this reaction is:

$2H^+(aq.)+2Br^-(aq.)+Co^{2+}(aq.)+2OH^-(aq.)\rightarrow Co^{2+}(aq.)+2Br^-(aq.)+H_2O(l)$

The net ionic equation becomes:

$H^+(aq.)+OH^-(aq.)\rightarrow H_2O(l)$

So, the correct option is 3.

4 0

2 years ago

Read 2 more answers

Determine the pH of a 2.8 ×10−4 M solution<br> of Ca(OH)2.

shepuryov [24]

Answer:

pH = 10.75

Explanation:

To solve this problem, we must find the molarity of [OH⁻]. With the molarity we can find the pOH = -log[OH⁻]

Using the equation:

pH = 14 - pOH

We can find the pH of the solution.

The molarity of Ca(OH)₂ is 2.8x10⁻⁴M, as there are 2 moles of OH⁻ in 1 mole of Ca(OH)₂, the molarity of [OH⁻] is 2*2.8x10⁻⁴M = 5.6x10⁻⁴M

pOH is

pOH = -log 5.6x10⁻⁴M

pOH = 3.25

pH = 14-pOH

3 0

2 years ago

An unknown or changeable quantity is called a(n)...

alexgriva [62]

I think the answer would be dependent variable. An unknown or changeable quantity is called a dependent variable. It <span>is what you measure in the experiment and what is affected during the experiment. Hope this answers the question. Have a nice day.</span>

6 0

2 years ago

A food web diagram is provided

Dmitriy789 [7]

the answer is D Grass>deer>mountain Lion

3 0

3 years ago