Can anyone help me with this answer?

B. 1.5 × 10⁻¹⁸

Step-by-step explanation:

Concept:

When multiplying exponents, add the exponents together.

When dividing exponents, subtract the exponents.

When converting scientific notation to an integer:

If the exponent is negative, move the decimal to the left with the same amount of units as the exponents. For example: If converting 5 × 10⁻³, since the exponent is -3, we move the decimal to the left 3 unitsIf the exponent is positive, move the decimal to the right with the same amount  of units as the exponentsFor example: If converting 2 × 10⁴, since the exponent is 4, we move the decimal to the right 4 units

When converting an integer to scientific notation:

If the number is ≥1, then count the moves of decimal point until the integer is 0<integer<10. The number of moves will be the exponent that is positive.For example: If converting 300, since there are two moves until it is left with 0<3<10. Thus, the scientific notation will be 3 × 10²If the number is <1, then count the moves of decimal point until the integer is 0<integer<10. The number of moves will be the exponent that is negative.For example: If converting 0.004, since there are three moves until it is left with 0<4<10. Thus, the scientific notation will be 4 × 10⁻³

Given:

Mass of one water molecule = 3.0 × 10⁻²³

Total number of molecules (required by the question) = 50,000

Solve:

Formula

Total mass = Mass of one water molecule × Total number of molecules

Substitute the values into the formula

Total mass = 3.0 × 10⁻²³ × 50,000

Convert 50,000 into scientific notation

Total mass = 3.0 × 10⁻²³ × 5 × 10⁴

Multiply numbers together/ Multiply exponents together

Total mass = 15 × 10⁻¹⁹ = 1.5 × 10⁻¹⁸

Hope this helps!! :)

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