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Goryan [66]
3 years ago
9

8th Grade Checkpoint 1

Chemistry
1 answer:
Bad White [126]3 years ago
8 0

Answer:

Antimony, Sb, an atom contains 51 protons inside the nucleus and 51 electrons outside the nucleus.

Explanation:

Option “C” is correct because protons exist inside the nucleus and electrons exist outside the nucleus. Moreover, Sb has the number of protons 51 that is found in the nucleus and it has 51 electrons that exist outside the nucleus. However, the nucleus contains protons and neutrons while electrons exist outside of the nucleus. All the given options do not follow such condition therefore, all the statements are incorrect accept option 3rd.

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What is the osmolarity of a solution made by dissolving 0.50 mole of the strong electrolyte cacl2 in 1.0 l of solution?
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Osmolarity=osmole  of  the  solute/litres  of  the  solution
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CaCl2--->Ca2+   +2Cl-
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What units are used to measure energy? A) volts B) angstroms C) centimeters D) joules
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A chemist measures the enthalpy change ?H during the following reaction: Fe (s) + 2HCl (g) ? FeCl2 (s) + H2 (g) =?H?157.kJ Use t
erik [133]

Correct Question:

A chemist measures the enthalpy change ΔH during the following reaction: Fe(s) + 2HCl(g)-->FeCl2(s) + H2 ΔH=-157.0 kJ. Use this information to complete the table below. Round each of your answers to the nearest kJ/mol

Answer:

-314 kJ

+628 kJ

+157 kJ

Explanation:

The enthalpy change of a reaction measures the amount of heat that is lost or gained by it. If ΔH >0 the heat is gained, and the reaction is called endothermic, if ΔH<0, the heat is lost, and the reaction is called exothermic.

If the reaction is inverted, the value of ΔH is inverted too (the opposite endothermic reaction is exothermic), and if the reaction is multiplied by a constant, ΔH will be multiplied by it too.

1) 2Fe(s) + 4HCl --> 2FeCl2(s) + 2H2(g)

This reaction is the product of the given reaction by 2, so

ΔH = 2*(-157) = -314 kJ

2) 4FeCl2(s) + 4H2(g) --> 4Fe(s) + 8HCl(g)

This reaction is the inverted reaction given multiplied by 4, so

ΔH = 4*(157) = +628 kJ

3) FeCl2(s) + H2(g) --> Fe(s) + 2HCl

This reaction is the inverted reaction given, so

ΔH = +157 kJ

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