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3 years ago

Round off or add zeros to the following calculated answers to give a final answer with three significant figures

1 answer:

8 0

In this case, 58.703 has five significant figures because the 3 at the end is significant and therefore makes the 0 significant as well. Since there are 5 significant figures, we need to round off the 7 to get 58.7, which has three significant figures.

Hope this helps.

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What is the symbol for decimeter

Marysya12 [62]

Answer:

The symbol for decimeter is dm

Explanation:

No need for an explanation

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3 years ago

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How many grams of Na2CO3 must be dissolved into 155g of water to create a solution with a molarity of 8.20 mol/kg

zhannawk [14.2K]

Answer:

135g Na2CO3

Explanation:

I'm going to assume you mean Molality which is mol solute/kg solvent

Molarity would be mol soute/ L solution

we know we have 155g of water which is .155 kg

essentially we have the equation:

mol/kg = 8.20

we substitute .155 in for kg and get:

mol/.155 = 8.20

Solving this gives mol = 1.271

now we must convert to grams using the molar mass

Molar mass Na2CO3 = 106G/mol

so to cancel moles we multiply:

1.271mol x 106g/mol

= 135g

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3 years ago

Help me out pls (image attached)

lubasha [3.4K]

Protons:13
neutrons:14
electrons:10

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3 years ago

Balance <br><br> _Mg + _HCL = _MgCl2 + H2

Pavel [41]

_Mg + _HCL = _MgCl2 + H2
Separate the terms on each side:

_Mg + _HCl = _MgCl2 + H2

Mg- 1 Mg-1

H-1 H-2

Cl-1 Cl-2

Mg is balanced on both sides so move on to the next (put a 1 in the space).

1Mg

There are two H's and two Cl's on the results side, so to balance the equation put a 2 as a coefficient for HCl and it'll all balance out.

2HCl

Balamced equation will be:

1Mg + 2HCL = 1MgCl2 + H2

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3 years ago

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What is the hydrogen ion concentration of a solution with pH=7.75 ?

Alja [10]

Answer:

$[H^+]=1.78x10^{-8}M$

Explanation:

Hello there!

In this case, according to the given information about the pH, it is firstly necessary for us to remember that the pH is defined as the potential of the hydrogen ions in the solution and the concentration of those ions represents how many of them are present in the solution; in such a way, it is possible for us use:

$pH=-log([H^+])$

Whereas the concentration of hydrogen ions can be calculated as follows:

$[H^+]=10^{-pH}$

So we plug in the given pH to obtain:

$[H^+]=10^{-7.75}=1.78x10^{-8}M$

Regards!

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3 years ago